added forgejo actions script

.forgejo/workflows/build-docusaurus.yml

@@ -0,0 +1,46 @@
+name: build-docusaurus
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: docker
+    steps:
+      - name: checkout repository
+        uses: https://code.forgejo.org/actions/checkout@v4
+
+      - name: setup node
+        uses: https://github.com/actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: restore cached dependencies
+        uses: https://code.forgejo.org/actions/cache/restore@v4
+        with:
+          path: |
+            ~/.npm
+            docusaurus/node_modules
+          key: ${{ runner.os }}-Docusaurus
+
+      - name: install dependencies
+        run: npm install --frozen-lockfile
+        working-directory: docusaurus
+
+      - name: build project
+        run: npm run build
+        working-directory: docusaurus
+
+      - name: capture build artifacts
+        uses: https://code.forgejo.org/forgejo/upload-artifact@v4
+        with:
+          name: docusaurus-artifacts.zip
+          path: docusaurus/build/
+          if-no-files-found: error
+
+      - name: cache downloaded dependencies
+        if: ${{ github.ref_name == github.event.repository.default_branch }}
+        uses: https://code.forgejo.org/actions/cache/save@v4
+        with:
+          path: |
+            ~/.npm
+            docusaurus/node_modules
+          key: ${{ runner.os }}-Docusaurus