Description

This adds initial support for exporting or copying a request flow as a web browser fetch command. I've specified the command as browser because I might decide to add an export for Node.js's fetch API in the future as well.

This covers basic GET and POST requests with text content, and escapes whitespaces, double-quotes to ", Unicode characters to \uXXXX.

Closes #4408.

TODO:

• Investigate how this interacts with form data
• Investigate how this interacts with files and blobs
• Investigate how this interacts with binary content - throws error if outside the Unicode range, escapes it otherwise
• Investigate how this interacts with CORS - You can't, since the browser is the one that enforces CORS
• Investigate how this interacts with f-string/escaping trickery

Please add more tests.

Checklist

• I have updated tests where applicable.
• I have added an entry to the CHANGELOG.