fix(docs): Change the return type of format function (docs & types) (#…

…751)

The return type was not updated when format function was changed to
an async function. This patch changes the type from `string` to
`Promise<string>`, this only affects language servers.

chore(prettier): Take Prettier 2.4.0's jsxBracketSameLine → bracketSa…

…meLine (#749)

BREAKING CHANGE: Support Prettier 2.4.0+

feat: ✨ Add TypeScript definitions (#739)

fix: 🐛 Support 'overrideConfigFile' option for ESLint (#745)