Bump athackst/mkdocs-simple-plugin from 2.3.0 to 3.1.0

Bumps [athackst/mkdocs-simple-plugin](https://github.com/athackst/mkdocs-simple-plugin) from 2.3.0 to 3.1.0.
- [Release notes](https://github.com/athackst/mkdocs-simple-plugin/releases)
- [Commits](athackst/mkdocs-simple-plugin@v2.3.0...v3.1.0)

---
updated-dependencies:
- dependency-name: athackst/mkdocs-simple-plugin
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/docs.yaml

@@ -14,4 +14,4 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
       - name: Build and push docs
-        uses: athackst/mkdocs-simple-plugin@v2.3.0
+        uses: athackst/mkdocs-simple-plugin@v3.1.0