docs: add breakpoint debugging guide

[theetrain]

Closes #7781, relates to #1144

• Add breakpoint debugging documentation to the 'appendix' section

While testing with the Node.js inspector, I tried to enable server-side breakpoint debugging, but was not successful. The sourcemaps are being generated, but only client-side code connect to chrome devtools. VSCode breakpoint debugging works well.

I'm hoping there could be a way to debug server-side code within chrome devtools as well, which would help developers who aren't using VSCode, but I'm unsure whose domain this falls in: SvelteKit, Vite, or something else.

---

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. Changesets that add features should be minor and those that fix bugs should be patch. Please prefix changeset messages with feat:, fix:, or chore:.

Edits

• Please ensure that 'Allow edits from maintainers' is checked. PRs without this option may be closed.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 5585533

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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

[benmccann]

I think it'd be helpful to make this npm run dev to match the text above and real projects so that the user can copy/paste this example

[theetrain]

Thanks, Ben! I also added a link to Svelte Inspector for good measure.

[Conduitry]

Proposed changes to the svelte.dev site need to target the svelte-4 branch, not main.

[Conduitry]

Apologies, I can't read. This is kit.

[benmccann]

Suggested change

	"name": "Run npm start",
	"name": "Run npm dev",

[benmccann]

Can we change the page prefix from 15- to 25-? I'd like to keep the integrations page coming first

[benmccann]

Suggested change

	With the build-in debug terminal, you can set up breakpoints in source files within VSCode.
	With the built-in debug terminal, you can set up breakpoints in source files within VSCode.