Add Tip about Push to Create project on New Project page

What does this MR do?

Adds a little tip that reveals a new feature shipped in 10.5: creating a new project straight from the command line (https://gitlab.com/gitlab-org/gitlab-ce/issues/26388).

Are there points in the code the reviewer needs to double check?

Couldn't use the Popover straight via markup only because when users clicked on copy link or the text box, the popover would close. Had to go via javascript triggering.

This way, the Popover isn't in the DOM when the .js-select-on-focus is added its listener (DOM ready).

I extracted the code that adds this behaviour to a utility file in the lib and import it to both places so I can apply it when needed.

Why was this MR needed?

Revealing a new feature to users at a good moment.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #42938 (closed)