feat: Add custom parsers testing helpers

[franky47]

This PR introduces a new export, with two functions to help testing custom parsers.

Parsers must be bijective, which means:

• On a valid input query string, running the parser then the serializer should output the same query string as the input
• On a valid state, running the serializer then the parser should return an identical value.

For that second point, identical value means that the eq equality function of the parser should return true when fed the input and output.

Usage

Eg, in Vitest:

import { testSerializeThenParse, testParseThenSerialize } from 'nuqs/testing'

testSerializeThenParse(parseAsInteger, 123)
expect(() => testSerializeThanParse(parseAsInteger, 3.14)).toThrow() // Not bijective: loss of precision

testParseThenSerialize(parseAsInteger, '123')
expect(() => testParseThenSerialize(parseAsInteger, '3.14')).toThrow()

Bug fix

Also contains a bug fix for date parsers which were missing a suitable equality function.

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Name	Status	Preview	Comments	Updated (UTC)
nuqs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 10, 2025 9:07am

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commit: 3963c53