same as harfbuzz hb_script_get_horizontal_direction.
We just hard-code the set of RTL script here, as it doesn't change often anyway.
The function is just syntactic sugar as it all does is basically looking up the
constant RTL_SCRIPTS set.
It's nice to have it here in a central place alongside 'script', 'script_name', etc.
`script_code` does the reverse of `script_name`: it takes a long
script name and returns a 4-letter script code.
Both `script_name` and `script_code` raise KeyError by default,
but can optionally return a default value instead.
The new `fontTools.unicodedata` module re-exports all the public
functions from the built-in `unicodedata` module, and also adds
additional functions.
The `script` function takes a unicode character and returns the
script name as defined in the UCD "Script.txt" data file.
It's implemented as a simple binary search, plus a memoizing
decorator that caches the results to avoid search the same
character more than once.
The unicodedata2 backport is imported if present, otherwise
the unicodedata built-in is used.
