feat: remove Markdownlint (#2298)

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## PR Checklist

- [x] Addresses an existing open issue: fixes #1926
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Now that `@eslint/markdown` is linting Markdown files and
`prettier-plugin-sentences-per-line` additionally formats them, there's
no more need for Markdownlint in this template.

This PR completely deletes `markdownlint`/`markdownlint-cli`, and adds
removal addons to `blockESLintMarkdown`. This reduces the count of
root-level files by two: `.markdownlint.json` and `.markdownlintignore`!

🎁

Author: JoshuaKGoldberg

.github/DEVELOPMENT.md

@@ -52,7 +52,6 @@ Each should be shown in VS Code, and can be run manually on the command-line:
 
 - `pnpm lint` ([ESLint](https://eslint.org) with [typescript-eslint](https://typescript-eslint.io)): Lints JavaScript and TypeScript source files
 - `pnpm lint:knip` ([knip](https://github.com/webpro/knip)): Detects unused files, dependencies, and code exports
-- `pnpm lint:md` ([Markdownlint](https://github.com/DavidAnson/markdownlint)): Checks Markdown source files
 - `pnpm lint:packages` ([pnpm dedupe --check](https://pnpm.io/cli/dedupe)): Checks for unnecessarily duplicated packages in the `pnpm-lock.yml` file
 - `pnpm lint:spelling` ([cspell](https://cspell.org)): Spell checks across all source files
 

.github/workflows/ci.yml

@@ -30,13 +30,6 @@ jobs:
       - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
       - uses: ./.github/actions/prepare
       - run: pnpm lint:knip
-  lint_markdown:
-    name: Lint Markdown
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
-      - uses: ./.github/actions/prepare
-      - run: pnpm lint:md
   lint_packages:
     name: Lint Packages
     runs-on: ubuntu-latest

.markdownlint.json

@@ -1,6 +1,5 @@
 {
 	"recommendations": [
-		"DavidAnson.vscode-markdownlint",
 		"dbaeumer.vscode-eslint",
 		"esbenp.prettier-vscode",
 		"streetsidesoftware.code-spell-checker",

.markdownlintignore

@@ -66,7 +66,6 @@ Thanks! 🎁
 <!-- spellchecker: disable -->
 <!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
 <!-- prettier-ignore-start -->
-<!-- markdownlint-disable -->
 <table>
   <tbody>
     <tr>
@@ -144,7 +143,6 @@ Thanks! 🎁
   </tbody>
 </table>
 
-<!-- markdownlint-restore -->
 <!-- prettier-ignore-end -->
 
 <!-- ALL-CONTRIBUTORS-LIST:END -->

.vscode/extensions.json

@@ -33,7 +33,6 @@ This table summarizes each block and which base levels they're included in:
 | Gitignore                          | `--add-gitignore`, `--exclude-gitignore`                                                   | ✔️      | ✅     | 💯         |
 | Knip                               | `--add-knip`, `--exclude-knip`                                                             |         |        | 💯         |
 | Main                               | `--add-main`, `--exclude-main`                                                             | ✔️      | ✅     | 💯         |
-| Markdownlint                       | `--add-markdownlint`, `--exclude-markdownlint`                                             |         |        | 💯         |
 | MIT License                        | `--add-mit-license`, `--exclude-mit-license`                                               | ✔️      | ✅     | 💯         |
 | ncc                                | `--add-ncc`, `--exclude-ncc`                                                               |         |        |            |
 | nvmrc                              | `--add-nvmrc`, `--exclude-nvmrc`                                                           |         |        | 💯         |
@@ -251,7 +250,6 @@ Using the _"everything"_ level will gain you comprehensive, strict coverage of a
 - [Lint ESLint](#lint-eslint)
 - [Lint JSDoc](#lint-jsdoc)
 - [Lint JSON](#lint-json)
-- [Lint MD](#lint-md)
 - [Lint Package JSON](#lint-package-json)
 - [Lint Packages](#lint-packages)
 - [Lint Perfectionist](#lint-perfectionist)
@@ -274,16 +272,6 @@ Using the _"everything"_ level will gain you comprehensive, strict coverage of a
 
 [`eslint-plugin-jsonc`](https://github.com/ota-meshi/eslint-plugin-jsonc): Adds linting for `.json` and `.jsonc` files.
 
-### Lint MD
-
-[**Markdownlint**](https://github.com/DavidAnson/markdownlint): Linting for Markdown code.
-
-```shell
-pnpm lint:md
-```
-
-> This is a separate linter from ESLint, but will likely eventually be switched to an ESLint plugin ([#567](https://github.com/JoshuaKGoldberg/create-typescript-app/issues/567)).
-
 ### Lint Package JSON
 
 [`eslint-plugin-package-json`](https://github.com/JoshuaKGoldberg/eslint-plugin-package-json): Linting for `package.json` files.

README.md

@@ -22,7 +22,6 @@
 		"format": "prettier .",
 		"lint": "eslint . --max-warnings 0",
 		"lint:knip": "knip",
-		"lint:md": "markdownlint \"**/*.md\" \".github/**/*.md\"",
 		"lint:packages": "pnpm dedupe --check",
 		"lint:spelling": "cspell \"**\" \".github/**/*\"",
 		"prepare": "husky",
@@ -99,8 +98,6 @@
 		"husky": "9.1.7",
 		"knip": "5.71.0",
 		"lint-staged": "16.2.7",
-		"markdownlint": "0.39.0",
-		"markdownlint-cli": "0.46.0",
 		"prettier": "3.7.3",
 		"prettier-plugin-curly": "0.4.1",
 		"prettier-plugin-packagejson": "2.5.20",