Add sinhala and tamil translations #491

I tested the banner of keepandroidopen.org and switched the language of the banner to sinhala, It did not work. Same goes to tamil

Sinhala:

Tamil:

Note: Sinhala's 2-letter language code is si. Tamil's 2-letter language code is ta

Website used to test the banner:
https://htmledit.squarefree.com/