Show code point in statusline

[jakoschiko]

This PR adds an option to show the code point under the cursor in the statusline. The code point is formatted using "U+" notation.

[archseer]

Do we need a persistent statusline element? We recently merged :character-info #4000

[jakoschiko]

My use case: Checking for unexpected characters after pasting text from the internet.

The statusline would be more convient because I can simply move the cursor while looking at the statusline. But the command would still improve my current situation.

[tgulacsi]

A copy-paste sometimes ends with \x00 - Vi shows it as ^@, helix as space.

echo -e "this is \\\\x00\x00:" | hx

the cursor vanishes over there, but my problem is that it is not shown that it is not a normal space.

[pascalkuthe]

I am going to close this as stale. I don't see us adding a statusline element for this as its fairly niche and we already have :character-info.

Thank you for contributing!