Add language icons to the language selector (#21298)

Closes https://github.com/zed-industries/zed/issues/21290

This is a first attempt to show the language icons to the selector.
Ideally, I wouldn't like to have yet another place mapping extensions to
icons, as we already have the `file_types.json` file doing that, but I'm
not so sure how to pull from it yet. Maybe in a future pass we'll
improve this and make it more solid.

<img width="700" alt="Screenshot 2024-11-28 at 16 10 27"
src="https://github.com/user-attachments/assets/683c3bef-5389-470f-a41e-3d510b927b61">

Release Notes:

- N/A

---------

Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>

crates/language/src/language.rs

@@ -129,6 +129,10 @@ pub static PLAIN_TEXT: LazyLock<Arc<Language>> = LazyLock::new(|| {
         LanguageConfig {
             name: "Plain Text".into(),
             soft_wrap: Some(SoftWrap::EditorWidth),
+            matcher: LanguageMatcher {
+                path_suffixes: vec!["txt".to_owned()],
+                first_line_pattern: None,
+            },
             ..Default::default()
         },
         None,
@@ -1418,6 +1422,10 @@ impl Language {
     pub fn prettier_parser_name(&self) -> Option<&str> {
         self.config.prettier_parser_name.as_deref()
     }
+
+    pub fn config(&self) -> &LanguageConfig {
+        &self.config
+    }
 }
 
 impl LanguageScope {