Sentry example: add js types to SentryWebpackPluginOptions (#28726)
* Add js types to SentryWebpackPluginOptions
Enables code completion in Visual Studio Code (and perhaps other editors)
* Use partial type for SentryWebpackPluginOptions
This matches the expected type in https://github.com/getsentry/sentry-javascript/blob/e71454ef781563e36c727315d1a5b59acb9e2e0a/packages/nextjs/src/config/webpack.ts#L38
* inline sentry config