Another tool to allow typing Arabic using English keyboard is given below, this one auto guesses and provides option, but does not write harkaat.
Yamli
1. Go to www.yamli.com/arabic-keyboard/
2. Start typing letters in english in transliteration style without vowels since it doesn't give harkaat.
3. e.g. you type 3nkbwt to get 3 suggestions عنكبوت
6. Also see https://writearabickeyboard.blogspot.com/2017/04/online-arabic-keyboard-type-arabic-using-english.html for detailed Arabic Keyboard.