fix: sanitize branch names for semantic-release prerelease (#1230)

The wildcard branch config was using `prerelease: true` which uses
the raw branch name as the prerelease identifier. Branch names with
underscores (e.g., leanplum_plugin_integration) are invalid per
SemVer spec and cause releases to fail.

Changed to `prerelease: 'beta'` so all non-master/non-support-branch
releases use 'beta' as the prerelease identifier, ensuring SemVer
compliance.

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: abueide

release.config.js

@@ -2,7 +2,7 @@ module.exports = {
   branches: [
     'master',
     { name: '+([0-9])?(.{+([0-9]),x}).x', prerelease: true }, // support branches (e.g., 1.x, 1.2.x)
-    { name: '*', prerelease: true }, // any other branch = prerelease
+    { name: '*', prerelease: 'beta' }, // any other branch = beta prerelease (fixes SemVer compliance)
   ],
   tagFormat: '${name}-v${version}',
   plugins: [