fix(ci): add contents:write permission to release workflow (#8)

The release workflow was failing with 403 when trying to create a GitHub
Release. This was caused by missing 'contents: write' permission which is
required by the softprops/action-gh-release action.

Other SDK repos (Go, Python) already have this permission configured.

Author: saurabhjain1592

.github/workflows/release.yml

@@ -5,6 +5,9 @@ on:
     tags:
       - 'v*'
 
+permissions:
+  contents: write
+
 jobs:
   release:
     runs-on: ubuntu-latest