Removes usage of yarn

We can still use yarn if we want but the lockfile will not be stored anymore.
The reason being that yarn does not work with the git hooks for
precommits we have setup. We could probably get it to work
but npm works already so one package manages is enough.

Author: gnikit

.github/workflows/main.yaml

@@ -13,14 +13,14 @@ jobs:
         with:
           node-version: ${{ matrix.node-version }}
       - name: Installing Extension
-        run: yarn install
+        run: npm ci
       - name: Compile
-        run: yarn compile
+        run: npm run compile
       - name: Linting
-        run: yarn lint
+        run: npm run lint
       - name: Test Syntax Highlighting
-        run: yarn test:grammar
+        run: npm run test:grammar
       - name: Test Unittests
         uses: GabrielBB/xvfb-action@v1
         with:
-          run: yarn test
+          run: npm test

CONTRIBUTING.md

@@ -11,5 +11,5 @@ First of all, this is a Visual Studio Code extension that uses TypeScript and to
 1. Fork the repo
 2. Clone your fork
 3. Create a branch
-4. Run `yarn install`
-5. To test the extension run `yarn test:grammar && yarn test`
+4. Run `npm install`
+5. To test the extension run `npm run test:grammar && npm test`