Bump actions/checkout from 2 to 2.3.4 (#56)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v2.3.4)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -40,7 +40,7 @@ jobs:
 
     steps:
       - name: Checkout source code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v2.3.4
 
       - name: Use Node.js
         uses: actions/[email protected]