feat: Slack notification after successful release

JIRA: PSDK-200
risk: low

Author: hkad98

.github/workflows/build-release.yaml

@@ -91,3 +91,17 @@ jobs:
           password: ${{ secrets.PYPI_API_TOKEN }}
           packages_dir: dist/${{ matrix.component }}
           verbose: true
+  slack-notification:
+    strategy:
+      matrix:
+        channels: [ "#releases" ]
+    runs-on: ubuntu-latest
+    needs: publish
+    steps:
+      - name: Notify to slack
+        uses: slackapi/slack-github-action@v1.25.0
+        with:
+          channel-id: ${{ matrix.channels }}
+          slack-message: "The release of *gooddata-python-sdk@${{ github.ref_name }}*, has been successful. :tada:"
+        env:
+          SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}