Extract PureScript support into an extension (#9824)

This PR extracts PureScript support into an extension and removes the
built-in PureScript support from Zed.

Release Notes:

- Removed built-in support for PureScript, in favor of making it
available as an extension. The PureScript extension will be suggested
for download when you open a `.purs` file.

crates/extensions_ui/src/extension_suggest.rs

@@ -39,6 +39,7 @@ pub fn suggested_extension(file_extension_or_name: &str) -> Option<Arc<str>> {
                 ("make", "Makefile"),
                 ("nix", "nix"),
                 ("prisma", "prisma"),
+                ("purescript", "purs"),
                 ("r", "r"),
                 ("r", "R"),
                 ("sql", "sql"),