electron-builder: Use core22 as snap base

[3v1n0]

By default electron-builder uses core18 as base, this is quite old at this point while core22 is the latest stable version and safer to use.

So use it as ferdium base.

It's also the same version where ferdium is built in CI.

Pre-flight Checklist

Please ensure you've completed all of the following.

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.

Description of Change

Motivation and Context

Screenshots

Checklist

• My pull request is properly named
• The changes respect the code style of the project (pnpm prepare-code)
• pnpm test passes
• I tested/previewed my changes locally

Release Notes

[mcmxcdev]

Nice one! Strange that electron-builder is using old core18 by default still.