Check extensions for param matcher files

[h8gi]

I get error messages ("Matcher names must match /^[a-zA-Z_][a-zA-Z0-9_]*$/ — "${file}" is invalid") when my emacs creates backup files (like #[id].js#) in /params directory.
I think only .js and .ts files should be included in matchers.

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with pnpm test and lint the project with pnpm lint and pnpm check

Changesets

• If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpm changeset and following the prompts. All changesets should be patch until SvelteKit 1.0

[changeset-bot]

🦋 Changeset detected

Latest commit: db5d543

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

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[PH4NTOMiki]

maybe it should be continue here? maybe i'm wrong

[h8gi]

Oh, I'm wrong! It should be continue.
I fixed it, thank you.

[Rich-Harris]

Thank you! I wonder if we should rename endpointExtensions to moduleExtensions and use it for this purpose as well?

[h8gi]

That sounds good!
For now, I rewrote ['.js', '.ts'] to endpointExtensions.

[benmccann]

For now, I rewrote ['.js', '.ts'] to endpointExtensions.

That's a bit confusing because you wouldn't expect endpointExtensions to affect matchers. I think you'd have to rename the option as well

[benmccann]

@h8gi it looks like this PR needs a rebase

[Rich-Harris]

thank you!