add tagbot

.github/workflows/TagBot.yml

@@ -0,0 +1,17 @@
+name: TagBot
+on:
+  issue_comment:  # THIS BIT IS NEW
+    types:
+      - created
+  workflow_dispatch:
+jobs:
+  TagBot:
+    # THIS 'if' LINE IS NEW
+    if: github.event_name == 'workflow_dispatch' || github.actor == 'JuliaTagBot'
+    # NOTHING BELOW HAS CHANGED
+    runs-on: ubuntu-latest
+    steps:
+      - uses: JuliaRegistries/TagBot@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          ssh: ${{ secrets.DOCUMENTER_KEY }}