Checks for existing `React` import before adding it automatically

[frencojobs]

Closes #96

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 71b069710edb7a9f5b30b66603b501ca1890bd71

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 9 packages

| Name | Type | | -------------------------------- | ----- | | shiki-twoslash | Patch | | eleventy-plugin-shiki-twoslash | Patch | | markdown-it-shiki-twoslash | Patch | | remark-shiki-twoslash | Patch | | docusaurus-preset-shiki-twoslash | Patch | | gatsby-remark-shiki-twoslash | Patch | | hexo-shiki-twoslash | Patch | | twoslash-cli | Patch | | vuepress-plugin-shiki-twoslash | Patch |

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