Move docs into subdirectory to make mkdocs work in a subdirectory

Signed-off-by: Tilman Vatteroth <tilman.vatteroth@tu-dortmund.de>

(cherry picked from commit eaeb88401d)
Signed-off-by: David Mehren <git@herrmehren.de>

docs/content/guides/auth/gitlab-self-hosted.md

@@ -0,0 +1,32 @@
+GitLab (self-hosted)
+===
+
+**Note:** *This guide was written before the renaming. Just replace `HackMD` with `CodiMD` in your mind :smile: thanks!*
+
+1. Sign in to your GitLab
+2. Navigate to the application management page at `https://your.gitlab.domain/admin/applications` (admin permissions required)
+3. Click **New application** to create a new application and fill out the registration form:
+
+![New GitLab application](../../images/auth/gitlab-new-application.png)
+
+4. Click **Submit**
+5. In the list of applications select **HackMD**. Leave that site open to copy the application ID and secret in the next step.
+
+![Application: HackMD](../../images/auth/gitlab-application-details.png)
+
+
+6. In the `docker-compose.yml` add the following environment variables to `app:` `environment:`
+
+```
+- CMD_DOMAIN=your.codimd.domain
+- CMD_URL_ADDPORT=true
+- CMD_PROTOCOL_USESSL=true
+- CMD_GITLAB_BASEURL=https://your.gitlab.domain
+- CMD_GITLAB_CLIENTID=23462a34example99XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+- CMD_GITLAB_CLIENTSECRET=5532e9dexamplXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+```
+
+7. Run `docker-compose up -d` to apply your settings.
+8. Sign in to your CodiMD using your GitLab ID:
+
+![Sign in via GitLab](../../images/auth/gitlab-sign-in.png)