Support `experimental.ts_syntax=true`

Per the [changelog for 0.229.0](https://github.com/facebook/flow/blob/main/Changelog.md#02290), enabling `experimental.ts_syntax=true` allows some TypeScript syntax, e.g., `Readonly` versus `$ReadOnly`.

This is a request for the option to be supported here, e.g., in [`require-readonly-react-props`](https://github.com/gajus/eslint-plugin-flowtype/blob/v8.0.3/src/rules/requireReadonlyReactProps.js#L16).

Start by reading src/rules/requireReadonlyReactProps.js, especially the location linked in the issue, and review how the rule handles $ReadOnly. Support the experimental.ts_syntax=true option for the requested TypeScript syntax, then verify the rule's behavior with the repository's existing checks.

Written by the indexing model from the issue text.