Feature: Introduce locale in web-widget SDK (#871)

* Introduce setLocale in SDK

Co-authored-by: Sojan <sojan@pepalo.com>

app/javascript/widget/api/specs/endPoints.spec.js

@@ -1,12 +1,14 @@
 import endPoints from '../endPoints';
 
+jest.mock('vue', () => ({ config: { lang: 'ar' } }));
+
 describe('#sendMessage', () => {
   it('returns correct payload', () => {
     const spy = jest.spyOn(global, 'Date').mockImplementation(() => ({
       toString: () => 'mock date',
     }));
     expect(endPoints.sendMessage('hello')).toEqual({
-      url: `/api/v1/widget/messages`,
+      url: `/api/v1/widget/messages?locale=ar`,
       params: {
         message: {
           content: 'hello',