Update CompatHelper to v3 (#490)

This is aimed at running the tests (in the new and improved "fail if the upgraded version wasn't used" manner). This package is holding back Observables, would be nice to fix.

Author: timholy

.github/workflows/CompatHelper.yml

@@ -1,19 +1,32 @@
 name: CompatHelper
-
 on:
   schedule:
-    - cron: '00 00 * * *'
-
+    - cron: 0 0 * * *
+  workflow_dispatch:
 jobs:
   CompatHelper:
     runs-on: ubuntu-latest
     steps:
-      - uses: julia-actions/setup-julia@latest
-        with:
-          version: 1.3
-      - name: Pkg.add("CompatHelper")
-        run: julia -e 'using Pkg; Pkg.add("CompatHelper")'
-      - name: CompatHelper.main()
+      - name: "Add the General registry via Git"
+        run: |
+          import Pkg
+          ENV["JULIA_PKG_SERVER"] = ""
+          Pkg.Registry.add("General")
+        shell: julia --color=yes {0}
+      - name: "Install CompatHelper"
+        run: |
+          import Pkg
+          name = "CompatHelper"
+          uuid = "aa819f21-2bde-4658-8897-bab36330d9b7"
+          version = "3"
+          Pkg.add(; name, uuid, version)
+        shell: julia --color=yes {0}
+      - name: "Run CompatHelper"
+        run: |
+          import CompatHelper
+          CompatHelper.main()
+        shell: julia --color=yes {0}
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: julia -e 'using CompatHelper; CompatHelper.main()'
+          COMPATHELPER_PRIV: ${{ secrets.DOCUMENTER_KEY }}
+          # COMPATHELPER_PRIV: ${{ secrets.COMPATHELPER_PRIV }}