fix: add Content-Type header for POST requests made by enhance

[allozaur]

This PR introduces passing the <form>'s enctype value or formSubmitter's formenctype value to Content-Type header for POST request made when executing the use:enhance function and a default¹ value of application/x-www-form-urlencoded when the <form> element doesn't have the enctype attribute specified or has an invalid value² provided.

When the enctype or formenctype is set to multipart/form then we don't provide the Content-Type header for fetch request

Close #1936

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Footnotes

1. https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/enctype ↩

2. https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#form-submission-attributes ↩

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Latest commit: a0d82a8

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[allozaur]

This is my first PR here so I'm sorry for any imperfections it might have 😅

I am not sure i got the changelog done right... besides that i think that the code is ready to be reviewed by a team member.

[eltigerchino]

Might want to also check why the ubuntu chromium tests are failing.

[allozaur]

@eltigerchino i've fixed up the tests for use:enhance and now i've got them all working :) i think that this PR is ready for reviewing and then adding it as a part of the next release ;)

[eltigerchino]

Thank you so much! This should be good to merge once CI passes (might need a few retries for the other flaky tests).