fix(ci): add explicit permissions to workflow

Set contents: read as minimum required permission for GITHUB_TOKEN.
Resolves code scanning alert #31.

Author: Yuriy Bezsonov

.github/workflows/ci.yml

@@ -13,6 +13,9 @@ on:
   pull_request:
     branches: [ "main" ]
 
+permissions:
+  contents: read
+
 jobs:
   build-java25:
     runs-on: ubuntu-latest