feat(editor): add syntax highlighting for go.mod and go.work files (#1695)

go.mod and go.work opened as plain text: their language definitions had no ui-mode, so no CodeMirror language loaded. Add a GoMod mode (a small stream parser): directives as keywords, module paths as strings, versions as numbers, // comments; shared by go.mod and go.work.

Co-authored-by: elfadl <[email protected]>

crates/ide-language/src/registry.rs

@@ -605,6 +605,7 @@ mod tests {
         "ERB",
         "JSP",
         "Astro",
+        "GoMod",
     ];
 
     fn reg() -> LanguageRegistry {