fix(sv): align eslint version to 10 accross all addons

[jonasgeiler]

Firstly, I apologize for not creating an issue before making this PR, I hope that's okay.
If you want I can still create and link an issue, instead of describing the problem in this PR.

Description

I have noticed that while creating a new project using the sv create command, and first selecting the eslint add-on, and afterwards selecting the prettier add-on (or just using the command pnpm dlx sv@0.15.1 create --template library --no-types --add eslint prettier --install pnpm example-project) that it always shows the following warning message:

An older major version of eslint was detected. Skipping eslint-config-prettier installation.

I thought that didn't make any sense, since I was creating a fresh new project, so I dug deeper and saw that the SUPPORTED_ESLINT_VERSION constant in the prettier.ts add-on definition had an outdated ESLint major version '9', which caused a version mismatch when installing it after the ESLint add-on.
Installing the Prettier add-on first didn't cause this problem, since the add-on script doesn't detect eslint yet and skips installing eslint-config-prettier, handing it over to the ESLint add-on, which happily installs eslint-config-prettier without checking it's own version.

I guess the problem was introduced in #989, where they bumped ESLint to v10, but forgot to update the (somewhat hidden) SUPPORTED_ESLINT_VERSION constant.

Now I could have just set the SUPPORTED_ESLINT_VERSION constant to '10' and call it a day, but I thought I'd rather future-proof this, so it doesn't happen again in the future.
For this, I have create a common ESLINT_VERSION constant (which I made sure also gets updated automatically by pnpm run update-deps), shared between the ESLint and Prettier add-ons.
The ESLint add-on just installs the version defined by that constant, but the Prettier add-on extracts the major version from that constant, and uses it in place of the previously hard-coded value.
I have also heavily modified the Prettier add-on tests, to make sure eslint-config-prettier gets installed, depending on the installed eslint version.

Checklist

• Update snapshots (if applicable)
• Add a changeset (if applicable)
• Allow maintainers to edit this PR
• I care about what I'm doing, no matter the tool I use (Notepad, Sublime, VSCode, AI...)

  Note: I have used GitHub Copilot's auto-complete feature for this contribution, however, no AI Agents where used. Most of the changes were written and double checked by myself, to the best of my knowledge.

[changeset-bot]

🦋 Changeset detected

Latest commit: f1be18a

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

This PR includes changesets to release 2 packages

Name	Type
@sveltejs/sv-utils	Patch
sv	Minor

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

[jycouet]

Thank you for your PR and looking at it.
Very well explained 👍

I let you have a look at the comments? Then will test it out

[pkg-pr-new]

Open in StackBlitz

npx https://pkg.pr.new/svelte-migrate@1069

npx https://pkg.pr.new/sv@1069

npx https://pkg.pr.new/@sveltejs/sv-utils@1069

commit: f1be18a

[jonasgeiler]

@jycouet Looking much better now! Nice work :)

[jycouet]

Thank you, you! :)

[hyunbinseo]

So eslint-config-prettier being removed in sv@0.13.0 was actually a bug?

• https://github.com/sveltejs/cli/releases/tag/sv%400.13.0
• hyunbinseo/svelte-kit-templates@1d5dbb1

[jycouet]

Probably due to this missing 9 to 10.

But it's here now: https://github.com/sveltejs/cli/blob/main/packages/sv/src/cli/tests/snapshots/create-with-all-addons/package.json#L42