Fix filtering TreeItem lists by non-ASCII strings
AssetFilter tries to normalize the TreeItem's text by removing any punctuation and symbols, but it was done using a simple [^a-zA-Z0-9\s] character class which removed any non-ASCII characters, breaking the search for many non-English languages. Replacing this with [^\w\s] didn't work, but iterating through the string and using isLetterOrNumber() does work.
Edited by Eric Jiang