Switch to using npm over yarn

Signed-off-by: Janne Savolainen <janne.savolainen@live.fi>

.github/workflows/mkdocs-manual.yml

@@ -37,8 +37,8 @@ jobs:
 
       - name: Generate Extensions API Reference using typedocs
         run: |
-          yarn install
-          yarn typedocs-extensions-api
+          npm install
+          npm run typedocs-extensions-api
 
       - name: Checkout master branch from lens
         uses: actions/checkout@v3