Z 2819 (#2872)

This PR adds new config option to language config called
`word_boundaries` that controls which characters should be recognised as
word boundary for a given language. This will improve our UX for
languages such as PHP and Tailwind.

Release Notes:

- Improved completions for PHP
[#1820](https://github.com/zed-industries/community/issues/1820)

---------

Co-authored-by: Julia Risley <julia@zed.dev>

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

@@ -10,3 +10,4 @@ brackets = [
     { start = "\"", end = "\"", close = true, newline = false, not_in = ["string"] },
 ]
 collapsed_placeholder = "/* ... */"
+word_characters = ["$"]