Bump actions/checkout from 2 to 2.3.4

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]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     name: Lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - uses: actions/setup-node@v2
         with:
           node-version: 15
@@ -24,7 +24,7 @@ jobs:
     name: Prettier
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - uses: actions/setup-node@v2
         with:
           node-version: 15
@@ -34,7 +34,7 @@ jobs:
     name: Flow
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - uses: actions/setup-node@v2
         with:
           node-version: 15
@@ -44,7 +44,7 @@ jobs:
     name: Test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - uses: actions/setup-node@v2
         with:
           node-version: 15
@@ -69,7 +69,7 @@ jobs:
           - windows-latest
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - uses: actions/setup-node@v2
         with:
           node-version: ${{ matrix.node_version }}
@@ -88,7 +88,7 @@ jobs:
     name: GitHub Pages
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - uses: actions/setup-node@v2
         with:
           node-version: 15
@@ -113,7 +113,7 @@ jobs:
     name: Publish
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - uses: actions/setup-node@v2
         with:
           registry-url: https://registry.npmjs.org/