Unfucked fetch

It's just fetch with a few DX improvements:

• Data is cached on the object once retrieved from the stream so it isn't destroyed (removes need to clone entire object for simple situations).

• Provides convenience 'gimme' method that will attempt to interpret data type based on headers and return data from relevant stream method.

• Each of these features are provided on a custom FkResponse with overloads for the data retrieval methods.

• Throws a fucking error. I prefer returned errors over throws too, they are the way errors should be done. BUT, when the rest of the language/ecosystem is built around throw/try-catch it makes things really, really annoying to have one common method that is different. Also not having a proper, ubiquitous option type kinda makes returned errors suck (still love you tho Go).

• Throws http-errors except for the custom NetworkError. If anyone knows of a better more TS friendly error lib I'll use that, or make my own.

• You can use fkFetch method directly the same as fetch or use createFkFetch to make your own instance with custom MIME type mapping.

• Decided not to Monkey-Patch fetch as this does change the use patterns considerably.

• Auto-capitalizes 'patch' to 'PATCH', because, come on... Nobody cares if it's not a standard verb, it's used nearly everywhere. The fact you have to point out in the docs that you must manually capitalize it is CLEAR a sign that it should be done automatically.