Add YAML-metadata for notes and change the document title accordingly (#310)

* Added yaml-frontmatter extracting and error handling
* add tests
* changed document-title, so the editor can change the title to the title of the yaml metadata. closes #303
* extracted first line parsing in a core rule of markdown-it
document title will now be determined like this:
1. yaml metadata title
2. opengraph title
3. first level one heading
4. 'Untitled'
* added documentTitle e2e test

Co-authored-by: Erik Michelson <github@erik.michelson.eu>
Co-authored-by: Philip Molares <philip@mauricedoepke.de>
Co-authored-by: Tilman Vatteroth <tilman.vatteroth@tu-dortmund.de>
Co-authored-by: mrdrogdrog <mr.drogdrog@gmail.com>

.github/workflows/build.yml

@@ -27,7 +27,7 @@ jobs:
           node-version: ${{ matrix.node }}
       - name: Install dependencies
         run: yarn install
-      - name: run unit tests
+      - name: Test Project
         run: yarn test
       - name: Build project
         run: yarn build