Fix Markdown files with Prettier and check in CI (#21972)

.github/workflows/lint-md.yml

+name: Markdown Linting
+on:
+  push:
+    branches-ignore:
+      - 'dependabot/**'
+    paths:
+      - '.github/workflows/lint-md.yml'
+      - '.prettier*'
+      - '**/*.md'
+      - '!AUTHORS.md'
+      - 'package.json'
+      - 'yarn.lock'
+
+  pull_request:
+    paths:
+      - '.github/workflows/lint-md.yml'
+      - '.prettier*'
+      - '**/*.md'
+      - '!AUTHORS.md'
+      - 'package.json'
+      - 'yarn.lock'
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Clone repository
+        uses: actions/checkout@v3
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v3
+        with:
+          cache: yarn
+
+      - name: Install all yarn packages
+        run: yarn --frozen-lockfile
+
+      - name: Prettier
+        run: yarn prettier --check "**/*.md"

.prettierignore

@@ -70,8 +70,8 @@ app/javascript/styles/mastodon/reset.scss
 # Ignore Javascript pending https://github.com/mastodon/mastodon/pull/23631
 *.js
 
-# Ignore Markdownlint pending https://github.com/mastodon/mastodon/pull/21972
-*.md
-
 # Ignore HTML till cleaned and included in CI
 *.html
+
+# Ignore the generated AUTHORS.md
+AUTHORS.md

CODE_OF_CONDUCT.md

@@ -8,19 +8,19 @@ In the interest of fostering an open and welcoming environment, we as contributo
 
 Examples of behavior that contributes to creating a positive environment include:
 
-* Using welcoming and inclusive language
-* Being respectful of differing viewpoints and experiences
-* Gracefully accepting constructive criticism
-* Focusing on what is best for the community
-* Showing empathy towards other community members
+- Using welcoming and inclusive language
+- Being respectful of differing viewpoints and experiences
+- Gracefully accepting constructive criticism
+- Focusing on what is best for the community
+- Showing empathy towards other community members
 
 Examples of unacceptable behavior by participants include:
 
-* The use of sexualized language or imagery and unwelcome sexual attention or advances
-* Trolling, insulting/derogatory comments, and personal or political attacks
-* Public or private harassment
-* Publishing others' private information, such as a physical or electronic address, without explicit permission
-* Other conduct which could reasonably be considered inappropriate in a professional setting
+- The use of sexualized language or imagery and unwelcome sexual attention or advances
+- Trolling, insulting/derogatory comments, and personal or political attacks
+- Public or private harassment
+- Publishing others' private information, such as a physical or electronic address, without explicit permission
+- Other conduct which could reasonably be considered inappropriate in a professional setting
 
 ## Our Responsibilities
 

CONTRIBUTING.md

-Contributing
-============
+# Contributing
 
 Thank you for considering contributing to Mastodon 🐘
 
@@ -28,9 +27,9 @@ You can submit translations via [Crowdin](https://crowdin.com/project/mastodon).
 
 Example:
 
-|Not ideal|Better|
-|---|----|
-|Fixed NoMethodError in RemovalWorker|Fix nil error when removing statuses caused by race condition|
+| Not ideal                            | Better                                                        |
+| ------------------------------------ | ------------------------------------------------------------- |
+| Fixed NoMethodError in RemovalWorker | Fix nil error when removing statuses caused by race condition |
 
 It is not always possible to phrase every change in such a manner, but it is desired.
 

SECURITY.md

@@ -2,7 +2,7 @@
 
 If you believe you've identified a security vulnerability in Mastodon (a bug that allows something to happen that shouldn't be possible), you can reach us at <security@joinmastodon.org>.
 
-You should *not* report such issues on GitHub or in other public spaces to give us time to publish a fix for the issue without exposing Mastodon's users to increased risk.
+You should _not_ report such issues on GitHub or in other public spaces to give us time to publish a fix for the issue without exposing Mastodon's users to increased risk.
 
 ## Scope