Guide to using Abhaya Libre in Sinhala

[pathumego]

Let's produce a small guide on how to use the font in Sinhala. Give special attention to document how to use the ligated conjunct, touch conjuncts and Opentype features. Use details from #57

[ravincaldera]

This is a good suggesion.

[pathumego]

@JanakaCB we are preparing to release a major new version of Abhaya Libre in September. Can we pickup this?