Add `ffl` and `tti` ligatures to Mona Sans

[LioraChen09]

Mona Sans currently includes ligatures such as ff, fi, fl, ffi, fy, tt, and ti, but it is missing ffl and tti.

Since f+f=ff, f+l=fl, t+t=tt, t+i=ti and ff+i=ffi already exist, adding ffl and tti would make the set more consistent and complete.
Example:

Additionally, please make sure that the new ligatures are compatible with ss01 and ss03.