Update TagBot setup and reduce frequency of CompatHelper to once per day (#475)

Author: giordano

.github/workflows/CompatHelper.yml

@@ -2,7 +2,7 @@ name: CompatHelper
 
 on:
   schedule:
-    - cron: '00 * * * *'
+    - cron: '0 0 * * *'
 
 jobs:
   CompatHelper:

.github/workflows/TagBot.yml

@@ -1,12 +1,15 @@
 name: TagBot
 on:
-  schedule:
-    - cron: 0 * * * *
+  issue_comment:
+    types:
+      - created
+  workflow_dispatch:
 jobs:
   TagBot:
+    if: github.event_name == 'workflow_dispatch' || github.actor == 'JuliaTagBot'
     runs-on: ubuntu-latest
     steps:
       - uses: JuliaRegistries/TagBot@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
-          ssh: ${{ secrets.TAGBOT_KEY }}
+          ssh: ${{ secrets.DOCUMENTER_KEY }}