editor: Recognize '$' as a Word character.

This fixes PHP variable completion. When we were querying for completions, PHP LS returned proper matches for variables which we filtered out as our query did not include a `$` character.

Z-2819

crates/language/src/buffer.rs

@@ -2987,7 +2987,7 @@ pub fn contiguous_ranges(
 pub fn char_kind(c: char) -> CharKind {
     if c.is_whitespace() {
         CharKind::Whitespace
-    } else if c.is_alphanumeric() || c == '_' {
+    } else if c.is_alphanumeric() || c == '_' || c == '$' {
         CharKind::Word
     } else {
         CharKind::Punctuation