Port some matchers from jest-extended

[silverwind]

Clear and concise description of the problem

jest-extended brings many useful additional matchers, and while it's already possible to use it to extend vitest's expect, I'm wondering if there is any willingness to include a few more basic matchers from it into vitest itself because jest-extended is rather heavyweight.

I'm primarily looking at very simple matchers like .toStartWith(prefix), .toInclude(substring) or the type matchers like .toBeNumber().

Suggested solution

Port over a few of the generally useful matchers from jest-extended.

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[sheremet-va]

What are "generally useful" matchers, and why should they be in a core? If community wants to have a light weight jest-extended package, let them create one. We might mention it in a docs.

[silverwind]

There are of course no hard rules on which matchers are generally useful, but for example

expect('string').toStartWith('string')

feels more "natural" because it's like String.prototype.startsWith. Compare to the regexp alternative vitest offers:

expect('string').toMatch(/^string/)

[silverwind]

Actually, jest-extended is already reasonably lightweight and with jest-community/jest-extended#520, it should now also not pull in jest any more via peerDependencies like it previously did.

So I'm personally happy with keeping it as a dependency with vitest.