Docs: Incorrect file extension

[henilshahdev]

What is the documentation issue?

File extension is incorrect. JavaScript files with JSX code should have the extension of .jsx instead of .js.

Is there any context that might help us understand?

It's a table under the Language and Filename section on the Contribution Guide.

Does the docs page already exist? Please link to it.

https://nextjs.org/docs/community/contribution-guide#language-and-filename