Add X social network icon

[jose-ardila]

Before submitting a new icon request, please confirm the following:

• I have searched all issues to make sure there isn't a request for this icon.
• I have searched the current library to make sure the icon doesn't already exist.
• I understand that brand icons are no longer being added and I can use SimpleIcons for my brand icon needs.
• I only intend to request a single icon (or a few near-identical ones) in this issue.

What would you use this icon for?

To use instead of the traditional twitter icon

Give us an example of what this icon might look like.

X

[MrGrigri]

Please refer to #6602 as we are removing all branded logos.