Created exercises

- Added endpoint to retrieve the list of exercises

app/Http/Controllers/ExerciseController.php

@@ -0,0 +1,18 @@
+<?php
+
+
+namespace App\Http\Controllers;
+
+
+use App\Exercise;
+
+class ExerciseController extends Controller
+{
+    /**
+     * Get the list of exercises
+     * @return \Illuminate\Http\JsonResponse
+     */
+    public function index() {
+        return response()->json(Exercise::all());
+    }
+}