fix: use actions/checkout@v2 in release action

Author: gr2m

lib/create-release-action.js

@@ -19,7 +19,7 @@ jobs:
     name: release
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@master
+      - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
           node-version: "12.x"