Added get_file backend

backend/get_file.php

+<?php
+
+header("Access-Control-Allow-Origin: *");
+header('Access-Control-Allow-Credentials: true');
+header("Access-Control-Allow-Methods: PUT, GET, POST, DELETE");
+header("Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept");
+header("Content-Type: application/json; charset=UTF-8");
+
+$postData = file_get_contents("php://input");
+$postData = json_decode($postData, true);
+
+$uname = $postData['username'];
+$f_path = $postData['file_path'];
+
+$path = "../users/" . $uname . "/" . $f_path;
+
+if(file_exists($path))
+{
+    echo json_encode(file_get_contents($path));
+}
+
+else
+{
+    http_response_code(404);
+}
+
+?>
\ No newline at end of file