Make build and testing more predictable

- Added missing files to .gitignore and added preventive measure to GHA
- Prevent accidental use of `npm install` or incorrect versions of
  yarn

Author: ssbarnea

.github/workflows/main.yml

@@ -28,6 +28,7 @@ jobs:
       - run: yarn test
         env:
           DISPLAY: ":99.0"
+      - run: if [[ -n $(git status --porcelain) ]]; then echo "repo is dirty, probably you missed to add some files to .gitignore"; fi
   package:
     runs-on: ubuntu-latest
     needs: test
@@ -43,6 +44,7 @@ jobs:
       - run: vsce package
       - run: echo "VSIX_PATH=$(find . -maxdepth 1 -type f -iname "*.vsix" | head -1)" >> $GITHUB_ENV
       - run: echo "VSIX_NAME=$(basename $(find . -maxdepth 1 -type f -iname "*.vsix" | head -1))" >> $GITHUB_ENV
+      - run: if [[ -n $(git status --porcelain) ]]; then echo "repo is dirty, probably you missed to add some files to .gitignore"; fi
       - uses: actions/upload-artifact@v4
         with:
           path: ${{ env.VSIX_PATH }}

.gitignore

@@ -6,4 +6,7 @@ node_modules
 *.vsix
 .DS_STORE
 *.log
-test-results.xml
+test-results.xml
+.yarn/install-state.gz
+.yarnrc.yml
+yarn.lock