Bump actions/checkout from 2.3.5 to 2.4.0 (#54)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2.3.5 to 2.4.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2.3.5...v2.4.0)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
   browsers:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
     - uses: actions/setup-node@v2.4.1
     - name: Install Dependencies
       run: npm install
@@ -28,7 +28,7 @@ jobs:
       matrix:
         node-version: [10, 11, 12, 13, 14, 15, 16]
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v2.4.1
       with:
@@ -44,7 +44,7 @@ jobs:
       matrix:
         node-version: [6, 8]
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v2.4.1
       with: