Add SSH key to TagBot workflow

Author: gragusa

.github/workflows/TagBot.yml

@@ -11,4 +11,5 @@ jobs:
     steps:
       - uses: JuliaRegistries/TagBot@v1
         with:
-          token: ${{ secrets.GITHUB_TOKEN }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+          ssh: ${{ secrets.DOCUMENTER_KEY }}