Move wiki inside the repository (#991)

Co-authored-by: Oleksii Holub <1935960+Tyrrrz@users.noreply.github.com>

.docs/Docker-usage-instructions.md

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+# Docker usage instructions
+
+Docker distribution of DiscordChatExporter provides a way to run the app in a virtualized and isolated environment. Due to the nature of Docker, you also don't need to install any prerequisites otherwise required by DCE.
+
+Note that only the CLI flavor of DiscordChatExporter is available for use with Docker.
+
+### Pulling
+
+This will download the [Docker image from the registry](https://hub.docker.com/r/tyrrrz/discordchatexporter) to your computer. You can run this command again to update when a new version is released.
+
+```
+docker pull tyrrrz/discordchatexporter:stable
+```
+
+Note the `:stable` tag. DiscordChatExporter images are tagged according to the following patterns:
+
+- `stable`: Latest stable version release and maps to the latest GitHub release. This tag is updated with release of each new version. Recommended for personal use.
+- `latest`: Built from the latest commit and maps to the latest CI build on GitHub. This tag is updated with each new commit to `master` branch. Not recommended for everyday use, but you can use it if you want to try out some features that haven't been officially released yet.
+- `x.y.z` (e.g. `2.30.1`): Fixed version release and maps to the corresponding tag on GitHub. This tag is never updated once that version has been released. Recommended for use in various automation scenarios.
+
+You can see all available tags [here](https://hub.docker.com/r/tyrrrz/discordchatexporter/tags?page=1&ordering=name).
+
+### Usage
+
+To run the CLI in Docker and render help text:
+
+```
+docker run --rm tyrrrz/discordchatexporter:stable
+```
+
+To export a channel:
+
+```
+docker run --rm -v /path/on/machine:/out tyrrrz/discordchatexporter:stable export -t TOKEN -c CHANNELID
+```
+
+If you want colored output, real-time progress reporting, and some other stuff, pass `-it` (interactive) option:
+
+```
+docker run --rm -it -v /path/on/machine:/out tyrrrz/discordchatexporter:stable export -t TOKEN -c CHANNELID
+```
+
+Note the `-v /path/on/machine:/out` option, which instructs Docker to bind the `/out` directory inside the container to a path on your host machine. Replace `/path/on/machine` with the directory you want the files to be saved at.
+
+**If you are running SELinux, you will need to add the `:z` option after `/out`, e.g.:**
+
+```
+docker run --rm -v /path/on/machine:/out:z tyrrrz/discordchatexporter:stable export -t TOKEN -c CHANNELID
+```
+
+For more information, refer to the [Docker docs SELinux labels for bind mounts page](https://docs.docker.com/storage/bind-mounts/#configure-the-selinux-label).
+
+You can also use the current working directory as the output directory by specifying:
+
+* `-v $PWD:/out` in Mac/Linux 
+* `-v $pwd.Path:/out` in PowerShell
+
+For more information, please refer to the [Dockerfile](https://github.com/Tyrrrz/DiscordChatExporter/blob/master/Dockerfile) and [Docker documentation](https://docs.docker.com/engine/reference/run/).<br>
+To get your Token and Channel IDs, please refer to [this page](https://github.com/Tyrrrz/DiscordChatExporter/blob/master/.docs/Obtaining-Token-and-Channel-IDs.md).
+
+### Environment variables
+
+DiscordChatExpoter CLI accepts environment variables as fallbacks for the `--token` and `--bot` options.
+
+- `DISCORD_TOKEN` to set the token
+- `DISCORD_TOKEN_BOT` to set whether it's a bot token (`true` or `false`)
+
+You can use these variables either with the `--env` Docker option or with a combination of the `--env-file` Docker option and a `.env` file.  
+Please refer to the Docker documentation for more information:
+
+* [Docker run - Set environment variables](https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e---env---env-file)
+
+### Permission issues with Linux hosts
+
+When bounding volumes between the container and the host, files mirrored from the Docker container will be owned by the Docker user (in most setups this is `root`). Please refer to this [issue comment](https://github.com/Tyrrrz/DiscordChatExporter/issues/800#issuecomment-1030471970) for instructions on how to override this behavior.
+
+### Build Docker images for arm on Raspberry Pi
+
+If you use the Docker image on arm (for example Raspberry Pi), you'd build the image as below.
+
+```bash
+$ git clone https://github.com/Tyrrrz/DiscordChatExporter.git
+$ cd DiscordChatExporter
+$ docker build -f DiscordChatExporter.Cli.dockerfile -t tyrrrz/discordchatexporter:latest .
+```
+
+After a while, some images are built like below.
+
+```bash
+$ docker image ls
+REPOSITORY                         TAG       IMAGE ID       CREATED              SIZE
+tyrrrz/discordchatexporter         latest    7c9ead725177   49 seconds ago       199MB
+<none>                             <none>    57f9f49d05af   About a minute ago   678MB
+mcr.microsoft.com/dotnet/sdk       5.0       72af6071941e   4 days ago           641MB
+mcr.microsoft.com/dotnet/runtime   3.1       6229bebd5a11   4 days ago           197MB
+```
+
+Among these, two images (`tyrrrz/discordchatexporter:latest` and `mcr.microsoft.com/dotnet/runtime:3.1`) are required, so you may delete the other two images.
+
+Now you can execute DiscordChatExporter:
+
+```bash
+$ docker run --rm tyrrrz/discordchatexporter:latest
+```
+
+___
+
+Special thanks to [@simnalamburt](https://github.com/simnalamburt) (dockerize) and [@Nimja](https://github.com/nimja) (better instructions)