Getting script of each code unit in an array

[mta452]

Currently, the script runs are identified in an iterating fashion. But sometimes an array turns out to be a better option to find out the overlapping regions of bidi runs and script runs. Technically it's not a big effort to write a utility function that fills out the script array by iterating over script runs. However, it would be really helpful if such a utility function is already provided in the library.

For example, it was a simpler approach for Java interoperability in Tehreer-Android. The relevant piece of code is available in ScriptClassifier.cpp