[9.x] Add new wrap string helper

[hebinet]

This PR adds a new wrap string helper.

Usage

Str:wrap('value')->wrap('"');
Str::of('value')->wrap('"');
str('value')->wrap('"');

// Outputs: "value"

Str:wrap('is', 'This ', ' me!');
Str::of('is')->wrap('This ', ' me!');
str('is')->wrap('This ', ' me!');

// Outputs: This is me!

Why do I think this is usefull?
Lately I had a Stringable class and modified its value like this:

$string = Str::of($path)
  ->lower()
  ->replaceLast('/')
  ->replaceFirst($host);

And I couldn't incorporate the wrapping fluently and had to do something like this:

$string = '"'.$string.'"';

...to further modify the string.

[TechyMS]

I think colon(':') is missing from Str:wrap.