Add GitHub workflow for markdownlint (#101)

* Add GitHub workflow for `markdownlint`

* Add `MD054` rule

* Add version numbers

* Simplify logic

- Only exclude `ŧranslated` files
- Only lint with `markdownlint-rule-titlecase`

* Lint all files, not only changed files

* Allow all HTML elements

.github/workflows/markdownlint.yml

@@ -0,0 +1,42 @@
+name: Run markdownlint
+
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - '**/*.md'
+      - '!translated/**'
+      - '!versions/*/translated/**'
+  workflow_dispatch: # Manual run
+
+concurrency:
+  group: markdownlint-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  markdownlint:
+    runs-on: ubuntu-22.04
+
+    steps:
+      - id: checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - id: node
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: .nvmrc
+
+      - id: titlecase
+        run: npm install [email protected]
+
+      - id: lint
+        uses: DavidAnson/markdownlint-cli2-action@v16
+        with:
+          config: .markdownlint-cli2.yaml
+          globs: |
+            **/*.md
+            !translated/**
+            !versions/*/translated/**

.markdownlint-cli2.yaml

@@ -0,0 +1,52 @@
+# Available configuration options: https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md
+config:
+  MD003:
+    style: atx
+  MD004:
+    style: dash
+  MD007:
+    indent: 2
+  MD009:
+    br_spaces: 0
+  MD013: false
+  MD024:
+    siblings_only: true
+  MD025:
+    front_matter_title: ""
+  MD026:
+    # Allow headings to end with `!`
+    punctuation: ".,;:。，；："
+  MD029:
+    style: ordered
+  MD033: false
+  MD035:
+    style: ---
+  MD044:
+    names:
+      - CurseForge
+      - Fabric
+      - GitHub
+      - Java
+      - Minecraft
+      - Modrinth
+      - Mojang
+    code_blocks: false
+  MD046:
+    style: fenced
+  MD048:
+    style: backtick
+  MD049:
+    style: underscore
+  MD050:
+    style: asterisk
+  MD053: false
+  MD054:
+    # these link styles are not easily localizable
+    collapsed: false  # A link to [keyword][].
+    shortcut: false   # A link to [keyword].
+                      # [keyword]: <https://example.com>
+    url_inline: false
+  MD055:
+    style: leading_and_trailing
+customRules:
+  - markdownlint-rule-titlecase