Summary

As it is, the documentation hints at the possibility of sending a request with a multipart form encoded body, but it is not explicit about it.

Hence it takes more time to figure it out on your own, especially for a less experienced developer.

This PR only adds 1 example in the multipart section of the quickstart page to demonstrate the process.

Checklist

• [X] I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• [ ] ~~I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.~~ Not applicable (only changed documentation)
• [X] I've updated the documentation accordingly.