feat: add `stringify` option

[masterHAWK99]

What kind of change does this PR introduce? (check at least one)

• [ ] Bugfix
• [x] Feature
• [ ] Code style update
• [ ] Refactor
• [ ] Build-related changes
• [ ] Other, please describe:

Does this PR introduce a breaking change? (check one)

• [ ] Yes
• [x] No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• [x] When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• [x] All tests are passing
• [x] New/updated tests are included

If adding a new feature, the PR's description includes:

• [ ] A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

Close #382

[masterHAWK99]

Thanks! Let's instead add a new option stringify that defaults to JSON.stringify. That way no breaking change

What do you mean? Changing the replacer parameter to stringify?

I came up with something like this:

export function mande(
  baseURL: string,
  stringify: (data: any) => string = JSON.stringify,
  passedInstanceOptions: OptionsRaw = {},
  fetchPolyfill?: Window['fetch']
): MandeInstance {

[posva]

No, let's keep the same arguments (non breaking) and add a new property to the options

[masterHAWK99]

Like that?

function _fetch(...) {
//...
if (method[0] === 'P' && data)
      mergedOptions.body = passedInstanceOptions.stringify
        ? passedInstanceOptions.stringify(data)
        : JSON.stringify(data)
}

export interface OptionsRaw<R extends ResponseAsTypes = ResponseAsTypes>
  extends Omit<Options<R>, 'headers' | 'signal'> {
 //...
  stringify?: (data: any) => string
}

[posva]

Yes

[posva]

Thanks, I couldn't push so I merged locally