Add comment about the workaround that was needed in the github workflow.

.github/workflows/main.yml

@@ -24,6 +24,10 @@ jobs:
     container:
       image: jf002/infinitime-build
     steps:
+      # This workaround fixes the error "unsafe repository (REPO is owned by someone else)".
+      # See https://github.com/actions/checkout/issues/760 and https://github.com/actions/checkout/issues/766
+      # The fix in "actions/checkout@v2" was not sufficient as the build process also uses git (to get the current
+      # commit hash, for example).
       - name: Workaround permission issues
         run: git config --global --add safe.directory "$GITHUB_WORKSPACE"
       - name: Checkout source files