Move plugins back to root dir

src-tauri/plugins/hello-world/greet.js

@@ -1,4 +0,0 @@
-export function greet() {
-  // Call Rust-provided fn!
-  sayHello('Plugin');
-}

src-tauri/plugins/hello-world/index.js

@@ -1,7 +0,0 @@
-import { greet } from './greet.js';
-
-export function hello() {
-  greet();
-  console.log('Try JSON parse', JSON.parse(`{ "hello": 123 }`).hello);
-  console.log('Try RegExp', '123'.match(/[\d]+/));
-}