fix(shell): make `execute` command async (#1362)

closes #1361

.changes/shell-execute.md

@@ -0,0 +1,5 @@
+---
+"shell": "patch"
+---
+
+Run `Command.execute()` JS api, asynchronously in the Rust side to avoid blocking main thread and causing the webview to freeze.

plugins/shell/src/commands.rs

@@ -186,7 +186,7 @@ pub struct ChildProcessReturn {
 
 #[allow(clippy::too_many_arguments)]
 #[tauri::command]
-pub fn execute<R: Runtime>(
+pub async fn execute<R: Runtime>(
     window: Window<R>,
     program: String,
     args: ExecuteArgs,