Update docs to recommend explicit controller names

Author: myabc

.github/copilot-instructions.md

@@ -135,7 +135,7 @@ Use Catalyst for component behaviors:
 ```typescript
 import {controller, target} from '@github/catalyst';
 
-@controller
+@controller('my-component')
 class MyComponentElement extends HTMLElement {
   @target button: HTMLElement
 

docs/contributors/adding-components.md

@@ -49,7 +49,7 @@ Catalyst has `controller` and `target` decorators which you have to import from
 ```ts
 import {controller, target} from '@github/catalyst';
 
-@controller
+@controller('my-component')
 class MyComponentNameElement extends HTMLElement {
   @target button: HTMLElement
 }