Glossary definitions for ijam and tashkil

I have created new definitions for ijam and tashkil at

https://r12a.github.io/scripts/glossary/#ijam
https://r12a.github.io/scripts/glossary/#tashkil

I'm hoping that the definition text is generally clearer, but i also 
changed the examples, since a hamza (in the old example) isn't really a 
tashkil, and that example had some other problems.

Fwiw, i adapted the definitions from 
https://r12a.github.io/scripts/arab/homographs.html#ijam_tashkil which 
i'm still working on, and removed the text in the Arabic orthography 
notes page that you previously pointed to.

If the new definitions look ok, next step will be to replace the 
definitions in the i18n WG glossary at
https://w3c.github.io/i18n-glossary/#def_ijam
https://w3c.github.io/i18n-glossary/#def_tashkil

ri