Fix search term match and highlight for Unicode chars

[Bizordec]

A regular expression /\w+/g was added in PR #307, which broke the search for non-english words.

I changed it to /\p{L}+/gu to add support for all Unicode characters and removed redundant word boundary (\b) in highlight regex.

[2bndy5]

Note

The search implementation will be changing completely upon merging #338; it will more closely follow upstream's behavior known as "the builtin search plugin". I doubt this hack would be needed after that. Furthermore, this hack might become more of a user customization.

[Bizordec]

Ok then, for now I'll rollback to v0.11.9, since this version has working search (but not highlighting) for Unicode.