(string-begins-with? string1 string2) -> boolean
Returns true if string1 begins with string2. Otherwise, returns false.
Examples:
>>(string-begins-with? "food" "f") :: #t
>>(string-begins-with? "food" "d") :: #f
>>(string-begins-with? "food" "fo") :: #t
Compare with: string-ends-with?