Allow any replacement or deletion

Hi,

Thank you for your work, nice lib !
Could you please add the capabilities to remove all emojis (and/or) replace with any char/string ?

```dart
 EmojiParser().replaceAll("...", "X");
 EmojiParser().removeEmojis("..."); // which could be EmojiParser().replace("...", "");
 // Deletion/replacement to empty string should remove double space if any :) 
```

Thanks !