🐛 Bug: content with GitHub flavoured alerts throws error

### Bug Report Checklist - [x] I have tried restarting my IDE and the issue persists. - [x] I have pulled the latest `main` branch of the repository. - [x] I have [searched for related issues](https://github.com/JoshuaKGoldberg/sentences-per-line/issues?q=is%3Aissue) and found none that matched my issue. ### Expected prettier runs without errors ### Actual ### Input ```md > [!NOTE] > These values are the list of possible `process.platform` values [documented by Node](https://nodejs.org/api/process.html#processplatform). ``` ### Prettier error ```txt Checking formatting... docs/rules/valid-os.md [error] docs/rules/valid-os.md: TypeError: Cannot read properties of undefined (reading 'start') [error] at Object.Yf [as print] (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/plugins/markdown.mjs:59:376) [error] at Object.print (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier-plugin-sentences-per-line@0.2.1_prettier@3.8.0/node_modules/prettier-plugin-sentences-per-line/lib/index.js:68:25) [error] at Object.apply (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/index.mjs:16309:24) [error] at callPluginPrintFunction (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/index.mjs:16631:20) [error] at mainPrintInternal (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/index.mjs:16611:18) [error] at mainPrint (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/index.mjs:16594:14) [error] at file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/index.mjs:14831:23 [error] at AstPath.each (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/index.mjs:14818:9) [error] at AstPath.map (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier@3.8.0/node_modules/prettier/index.mjs:14830:10) [error] at Object.print (file:////eslint-plugin-package-json/node_modules/.pnpm/prettier-plugin-sentences-per-line@0.2.1_prettier@3.8.0/node_modules/prettier-plugin-sentences-per-line/lib/index.js:59:14) ``` ### Additional Info _No response_