Used by the word movement keys (e.g. alt+backspace) to find a word break.
See Implementation
Added April 21, 2021 (dub v9.5)
Prior to that, LineGetter only used std.uni.isWhite. Now it uses this which uses if not alphanum and not underscore.
You can subclass this to customize its behavior.
Used by the word movement keys (e.g. alt+backspace) to find a word break.