Add initial package.json scripts task autodetection (#32497)

Now, every JS/TS-related file will get their package.json script
contents added as tasks:

<img width="1020" alt="image"
src="https://github.com/user-attachments/assets/5bf80f80-fd72-4ba8-8ccf-418872895a25"
/>

To achieve that, `fn associated_tasks` from the `ContextProvider` was
made asynchronous and the related code adjusted.

Release Notes:

- Added initial `package.json` scripts task autodetection

---------

Co-authored-by: Piotr Osiewicz <piotr@zed.dev>

crates/language/src/task_context.rs

@@ -1,6 +1,6 @@
 use std::{ops::Range, path::PathBuf, sync::Arc};
 
-use crate::{LanguageToolchainStore, Location, Runnable};
+use crate::{File, LanguageToolchainStore, Location, Runnable};
 
 use anyhow::Result;
 use collections::HashMap;
@@ -39,10 +39,11 @@ pub trait ContextProvider: Send + Sync {
     /// Provides all tasks, associated with the current language.
     fn associated_tasks(
         &self,
-        _: Option<Arc<dyn crate::File>>,
-        _cx: &App,
-    ) -> Option<TaskTemplates> {
-        None
+        _: Arc<dyn Fs>,
+        _: Option<Arc<dyn File>>,
+        _: &App,
+    ) -> Task<Option<TaskTemplates>> {
+        Task::ready(None)
     }
 
     /// A language server name, that can return tasks using LSP (ext) for this language.