ci: bump actions/checkout from 2.4.0 to 3 (#192)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2.4.0 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2.4.0...v3)

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

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.yaml

@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 20
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
           node-version-file: .nvmrc

.github/workflows/markdown-link-check.yaml

@@ -12,7 +12,7 @@ jobs:
     name: Check Markdown links
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3
       - uses: gaurav-nelson/[email protected]
         with:
           use-quiet-mode: 'yes'