Add word_characters to language overrides & use for more things

Use word_characters to feed completion trigger characters as well and
also recognize kebab as a potential sub-word splitter. This is fine for
non-kebab-case languages because we'd only ever attempt to split a word
with a kebab in it in language scopes which are kebab-cased

Co-Authored-By: Max Brunsfeld <max@zed.dev>

crates/zed/src/languages/javascript/config.toml

@@ -17,3 +17,6 @@ brackets = [
 [overrides.element]
 line_comment = { remove = true }
 block_comment = ["{/* ", " */}"]
+
+[overrides.string]
+word_characters = ["-"]