Set explicit permissions for GitHub Actions workflows (#261)

This change was made by an automated process to ensure all GitHub Actions workflows have explicitly defined permissions as per best practices.

Author: picatz

.github/workflows/ci.yml

@@ -1,4 +1,7 @@
 name: Continuous Integration
+permissions:
+  contents: read
+  actions: write
 on: # rebuild any PRs and main branch changes
   pull_request:
   push: