release-basetools.yml: Add contents write permission for publishing

The GITHUB_TOKEN is used in the `gh release upload` command to
upload a new basetools release. This adds content write permission
to allow the upload to work when the default permission is read-only
for the token.

Signed-off-by: Michael Kubacki <[email protected]>

.github/workflows/release-basetools.yml

@@ -101,6 +101,10 @@ jobs:
     needs: build
     if: github.event_name == 'release'
     runs-on: ubuntu-latest
+
+    permissions:
+      contents: write
+
     steps:
       - name: Checkout Code
         uses: actions/checkout@v4