Upgrade command: Keep `package.json` version prefix

[lcnvdl]

When you create a new FoalTS project, all @foal dependencies begins with the '^' prefix. I think maybe it's a good idea to keep it.

See the NPM docs and semver docs:

~version “Approximately equivalent to version”, will update you to all future patch versions, without incrementing the minor version. ~1.2.3 will use releases from 1.2.3 to <1.3.0.

^version “Compatible with version”, will update you to all future minor/patch versions, without incrementing the major version. ^1.2.3 will use releases from 1.2.3 to <2.0.0.

Issue

Version prefix is lost after upgrading Foal with the command foal upgrade.

Solution and steps

Checklist

• [x] Add/update/check docs (code comments and docs/ folder).
• [x] Add/update/check tests.
• [x] Update/check the cli generators.