title: Cannot create property 'validator' on string 'sendUs'
body: <p>I'm trying to work with an Angular Material package for entering and validating international telephone numbers which is ngx-mat-intl-tel-input and in order to do that, i had to work with the form group but i'm having the following error : </p>
  
  <pre><code>Cannot create property 'validator' on string 'sendUs'
  </code></pre>
  
  <p>Here is my code html : </p>
  
  <pre><code>  &lt;div class="bo4 of-hidden size15 m-b-20"&gt;
       &lt;form [formGroup]="'sendusForm'"&gt;
            &lt;input type="text" formControlName="phone"&gt;
        &lt;/form&gt;
    &lt;/div&gt;
  </code></pre>
  
  <p>and here is my typescript file :</p>
  
  <pre><code>import { Component, OnInit } from '@angular/core';
  import { FormGroup, FormBuilder, Validators } from '@angular/forms';
      export class HomeComponent implements OnInit {
        sendusForm: FormGroup;
        constructor(private formBuilder: FormBuilder)   {
        }
  
        ngOnInit() {
          this.sendusForm = this.formBuilder.group({
            phone: ['',  [Validators.required]]
          });
        }
  
        get f() { return this.sendusForm.controls; }
      }
  </code></pre>
  
  <p>Please can you help me solve this probleme.</p>