ci: set main branch as valid semantic release branch

Author: Belco90

package.json

@@ -21,7 +21,21 @@
     "url": "https://github.com/testing-library/eslint-plugin-testing-library/issues"
   },
   "release": {
-    "pkgRoot": "dist"
+    "pkgRoot": "dist",
+    "branches": [
+      "+([0-9])?(.{+([0-9]),x}).x",
+      "main",
+      "next",
+      "next-major",
+      {
+        "name": "beta",
+        "prerelease": true
+      },
+      {
+        "name": "alpha",
+        "prerelease": true
+      }
+    ]
   },
   "main": "index.js",
   "scripts": {