Add telegram notification to build workflow

.forgejo/workflows/build.yaml

@@ -16,3 +16,13 @@ jobs:
         with:
           push: true
           tags: git.korhonen.cc/functionalhacker/forgejo-asciidoc
+      - name: Notify in Telegram channel
+        uses: appleboy/telegram-action@master
+        with:
+          to: "-1001915202306"
+          token: ${{ secrets.TELEGRAM_TOKEN }}
+          message: |
+            Newest version of Forgejo with AsciiDoc support
+            has just been built. `docker pull` way!
+
+            See details: https://git.korhonen.cc/${{ github.repository }}/actions/${{ github.workflow }}