Unicode property `Joining_Group` is not exposed by this library.

[asibahi]

Title sums it up. The Unicode properties of Joining_Type and Joining_Group are not exposed (or not implemented?) by this library, which gives dealing with Arabic script text a bit more friction than it needs. Meanwhile, rust users can use the unicode_joining_type crate.

[sffc]

This is a good first issue. Adding it should be similar to adding Hangul_Syllable_Type which I did last week:

https://github.com/unicode-org/icu4x/pull/4885

[hsivonen]

Joining_Type is already available in icu_properties 1.4.2 and 1.5.

[asibahi]

I tried a couple of weeks back to add it like in these commits, but the crate structure seems to have changed significantly. Unfortunately, the crate structure proved to be too complex for me to grok it.