<ifModule mod_rewrite.c>

  RewriteEngine on

  # If file or directory exists behave normally
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d

  # Otherwise use index.html (you might need to update path)
  RewriteRule ^.*$ /index.html [L,QSA]

</ifModule>