Improve grammar, typos in editor-setup.mdx

[rmschindler]

Change title case to be consistent with other titles; fix minor grammatical issues.

[github-actions[bot]]

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[ranile]

@rmschindler there are two PRs with the same title: #3482 (this one) and #3481. Which one should be reviewed? Can you also please close one the one that's not supposed to be reviewed?

[rmschindler]

@hamza1311, both PRs are valid. PR #3482 pertains to editor-setup.mdx, PR #3481 pertains to introduction.mdx. Thank you.