Switch to using npm over yarn

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

.github/workflows/main.yml

@@ -34,12 +34,12 @@ jobs:
 
       - name: Generate Extensions API Reference using typedocs
         run: |
-          yarn install
-          yarn run build:docs
+          npm install
+          npm run build:docs
 
       - name: Verify that the markdown is valid
         run: |
-          yarn run mkdocs:verify
+          npm run mkdocs:verify
 
   build:
     name: Deploy docs
@@ -77,8 +77,8 @@ jobs:
 
       - name: Generate Extensions API Reference using typedocs
         run: |
-          yarn install --frozen-lockfile
-          yarn build:docs
+          npm ci
+          npm run build:docs
 
       - name: mkdocs deploy master
         if: contains(github.ref, 'refs/heads/master')