Using this URL instead worked for me : "*https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.11.2/css/all.css*"

Just add it to your index.css :

@import url('https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.11.2/css/all.css');

OR

to your index.html (inside tag) :

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">