add GitHub workflows

.github/workflows/discord.yml

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+name: Discord Notification
+
+on:
+  workflow_run:
+    workflows: ['CI', 'Docs']
+    types: [completed]
+
+jobs:
+  notify:
+    # if: ${{ github.event.workflow_run.conclusion == 'failure' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Push the notification using Discord webhook
+        env:
+          # 🟢 has poor compatibility: https://www.unicompat.com/1F7E2
+          CI_STATUS: ${{ github.event.workflow_run.conclusion == 'success' && '✅' ||  github.event.workflow_run.conclusion == 'failure' && '🔴' || github.event.workflow_run.conclusion }}
+          REPO_NAME: ${{ github.event.repository.name }}
+          GIT_BRANCH: ${{ github.event.workflow_run.head_branch }}
+          WORKFLOW_NAME: ${{ github.event.workflow_run.name }}
+          WORKFLOW_URL: ${{ github.event.workflow_run.conclusion == 'failure' && github.event.workflow_run.html_url || '' }}
+          DISCORD_WEBHOOK: ${{ secrets.DISCORD_WEBHOOK }}
+        # Playground: https://gist.github.com/brillout/da1ab713bda6e3c0d2ad909c1a4e80f2
+        run: |
+          curl \
+            -i \
+            -H "Accept: application/json" \
+            -H "Content-Type:application/json" \
+            -X POST \
+            --data "{\"content\":\"$CI_STATUS $REPO_NAME $WORKFLOW_NAME $GIT_BRANCH $WORKFLOW_URL\",\"username\":\"GitHub\",\"avatar_url\":\"https://i.imgur.com/OOtUMJD.png\"}" \
+            $DISCORD_WEBHOOK
+      - name: Debug/inspect
+        env:
+          EVENT: ${{ toJSON( github.event ) }}
+        run: echo $EVENT

.github/workflows/formatting.yml

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+name: 'Check formatting'
+on:
+  push:
+jobs:
+  check_formatting:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: pnpm/action-setup@v3
+      - run: pnpm install
+      - run: pnpm run format:check
+