refactor: shorten react import regex pattern

[StyleShit]

I came to this repo to read how it works under the hood and noticed that this regex pattern can be shortened.
Well... it's nitpicking and probably doesn't really matter, I just thought it could be easier to read.
I also saw a slight improvement in performance on my machine (which might be negligible and considered a redundant micro-optimization, but still 😅).

Regex Test
Regex Benchmark

Thank you for maintaining it! 😄

[ArnaudBarre]

Hi!
Thanks the use of \b seems legit here.
The perf gain will be only for people using the classic runtime which should be low I hope now.
@sapphi-red WDYT?

[sapphi-red]

The new regex will match more cases (e.g. import foo from 'foo'; import React from 'react') and I guess it'd fix some edge cases, too.