Add markdown linting (without breaking the site this time!)

.github/workflows/markdownlint.yml

@@ -0,0 +1,19 @@
+name: 'Lint Markdown'
+on: 
+  pull_request:
+    types: [opened, synchronize]
+
+jobs:
+  lint-markdown:
+    name: Lint markdown
+    runs-on: ubuntu-latest
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v2
+
+    - name: Lint markdown files
+      uses: docker://avtodev/markdown-lint:v1 # fastest way
+      with:
+        config: '.markdownlint.yaml'
+        args: '**/*.md'
+        ignore: '_snippets' # multiple files must be separated with single space

.github/workflows/mkdocs-build-sanity-check.yml

@@ -0,0 +1,24 @@
+name: 'mkdocs sanity check'
+on: 
+  pull_request:
+    types: [opened, synchronize]
+
+jobs:
+  mkdocs-sanity-check:
+    name: Check mkdocs builds successfully
+    runs-on: ubuntu-latest
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v2
+
+    - name: Set up Python 3.8
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+        architecture: x64
+
+    - name: Install requirements
+      run: python3 -m pip install -r requirements.txt
+
+    - name: Test mkdocs builds
+      run: python3 -m mkdocs build

.github/workflows/prune-stale-issues-prs.yml

@@ -10,6 +10,6 @@ jobs:
     - uses: actions/stale@v3
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
-        stale-issue-message: 'This issue has gone mouldy, because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days'
-        days-before-stale: 30
-        days-before-close: 5
+        stale-issue-message: 'This issue has gone mouldy, because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 14 days'
+        days-before-stale: 90
+        days-before-close: 14