Update URLs and logos with X design (former Twitter)

[aescanes]

Update URLs and logos with X design (former Twitter). Now that we can use fontawesome-6, this change should be easy.
I can create a fork and work on this if you guys agree.

https://fontawesome.com/icons/x-twitter?f=brands&s=solid

[Whydidthechickencrosstheroad]

Yeah, I noticed that it was not updated a little while since the update logo with X (or Twitter I should say)

[unrealapex]

I'll shoot a PR to fix this.

[Whydidthechickencrosstheroad]

It still hasn't been finished

[unrealapex]

#5541

Discussing with Miodec, we decided that it was best to continue referring to X as Twitter on the site, but the all the links are now updated to x.com. Also FYI the current version of Font Awesome that Monkeytype uses doesn't have X's icon.