feat: Add ability to bulk import contacts (#3026)

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/javascript/dashboard/api/contacts.js

@@ -52,6 +52,14 @@ class ContactAPI extends ApiClient {
     )}`;
     return axios.get(requestURL);
   }
+
+  importContacts(file) {
+    const formData = new FormData();
+    formData.append('import_file', file);
+    return axios.post(`${this.url}/import`, formData, {
+      headers: { 'Content-Type': 'multipart/form-data' },
+    });
+  }
 }
 
 export default new ContactAPI();