feat: add support for external plugins and enhance plugin management

crates/plugins/plugin-calc/src/lib.rs

@@ -1,5 +1,5 @@
 use async_trait::async_trait;
-use k_launcher_kernel::{LaunchAction, Plugin, PluginName, ResultId, ResultTitle, Score, SearchResult};
+use k_launcher_kernel::{LaunchAction, Plugin, ResultId, ResultTitle, Score, SearchResult};
 
 pub struct CalcPlugin;
 
@@ -26,7 +26,7 @@ fn should_eval(query: &str) -> bool {
 
 #[async_trait]
 impl Plugin for CalcPlugin {
-    fn name(&self) -> PluginName {
+    fn name(&self) -> &str {
         "calc"
     }