Start switching over files to typescript

src/App.jsx

@@ -1,7 +1,7 @@
 import React, {Component} from 'react';
 
 import './App.scss';
-import {declineSaimiar} from './saimiar_morphology.js';
+import {declineSaimiar} from './saimiar_morphology.ts';
 
 const backendUrl = 'https://kucinakobackend.ichigo.everydayimshuflin.com';