Move Gitea workflows to repository root

.gitea/workflows/build.yml

@@ -0,0 +1,40 @@
+name: Build
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: opera-cache-cleaner-extension
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Check background script syntax
+        run: node --check background.js
+
+      - name: Check popup script syntax
+        run: node --check popup/popup.js
+
+      - name: Build extension archive
+        shell: bash
+        run: |
+          rm -rf dist
+          mkdir -p dist/package
+          cp manifest.json background.js dist/package/
+          cp -R popup icons dist/package/
+          cd dist/package
+          zip -r ../opera-cache-cleaner-extension.zip .
+
+      - name: Upload extension archive
+        uses: actions/upload-artifact@v3
+        with:
+          name: opera-cache-cleaner-extension
+          path: opera-cache-cleaner-extension/dist/opera-cache-cleaner-extension.zip