Add a new function to convert a base64 string to a dynamic array of 0-255 values
Currently there is a function to convert a base64 string to utf8 string i.e. base64_decodestring. However if there is no valid string output, that function fails and returns nothing.
e.g. print base64_decodestring("igAAAAAAAACDAAAAACAAAA==")
There are cases where we need a byte representation of a base64 string. Having a function like base64_decodearray that gives a dynamic array of 0-255 values allows us to get that.