Add [skip publish] support to publish workflow (#90)

When a commit message on main contains [skip publish], the publish
workflow will skip the NuGet push. Useful for doc updates or batching
multiple PRs before a release.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jaredpar

.github/workflows/publish.yml

@@ -17,7 +17,9 @@ jobs:
     runs-on: ubuntu-latest
     if: >-
       github.event_name == 'workflow_dispatch' ||
-      (github.event_name == 'workflow_run' && github.event.workflow_run.conclusion == 'success')
+      (github.event_name == 'workflow_run' && 
+       github.event.workflow_run.conclusion == 'success' &&
+       !contains(github.event.workflow_run.head_commit.message, '[skip publish]'))
     steps:
       - uses: actions/checkout@v4
         with: