Restrict GITHUB_TOKEN permissions to contents: read

Agent-Logs-Url: https://github.com/dennisdoomen/CSharpGuidelines/sessions/be493e29-c6b7-45c4-ad17-0f4eb771419f

Co-authored-by: dennisdoomen <572734+dennisdoomen@users.noreply.github.com>

Author: Copilot

.github/workflows/build.yml

@@ -9,6 +9,8 @@ on:
 jobs:
   build:
     runs-on: windows-latest
+    permissions:
+      contents: read
 
     steps:
       - uses: actions/checkout@v4