feat: Refactor Response class and add new initialization methods

[gaetschwartz]

Changes

• Add default response status and status text in the Response constructors
• Add Response.jsify method for initializing Response with a JS object as body
• Separate Response.json method from Response.jsify for initializing Response with a JSON-encodable object as body
• Add documentation for main the constructors of Response

Motivation

jsify is subject to minification and has somewhat bad performance. When using dart compile with minification enabled, the response json gets minified (after a certain depth AFAIK). It should not be the case. The new Response.json behaves simlarly from the previous implementation except that it doesn't minify as it uses json.encode. Renamed the previous implementation to Response.jsify as it could still be useful for some cases.

[Ehesp]

@gaetschwartz thanks for this - what's the use case for the jsify method?

[gaetschwartz]

Well, as jsify can translate Dart objects to Js objects directly, people could still have some use. As it was the old behavior I figured I would leave it.

[rrousselGit]

I'm not really familiar with the project, but it looks alright at a quick glance.

I'd still consider this a breaking change (since the "json" constructor changes). And it'd be great to have some tests. But the project doesn't seem to have some atm, so that's alright I guess