Task $1$

Complete the ParseOnWS$()$ function so that it:

splits a string document by whitespace characters, i$.$e$.,($space$),\backslash$t $($tab$),$

$($newline$),\backslash$r $($carriage return$),$ into a list of string tokens.

if specified, lowercases the string before tokenizing it so the returned list of string tokens is lowercased.