feat(nextjs): Add option to have TS sentry config files, other small fixes

[lobsterkatie]

This documents the change in getsentry/sentry-javascript#3847, which allows for TypeScript versions of sentry.server.config.js and sentry.client.config.js, by adding TypeScript versions of those files to the code blocks.

It also includes a few other small fixes:

• Also add a Typescript version of the withSentry code snippet, both on the manual setup page and the getting started page.
• Move the alert about not supporting the serverless target into the section about next.config.js, which is where it's relevant.
• Remove the split between the snippet for sentry.server.config.js and sentry.client.config.js, as they were the exact same code. Instead, both filenames are listed on the snippet.
• Add filenames to the two next.config.js snippets which were missing them.
• Let the autoformatter do its thing.

[vercel]

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