Update README note about SF3 support

[mawe42]

The README of this project still states that only MuseScore can load and play SF3 files. Maybe it would be good to update that and also mention at least Fluidsynth (SF3 support stable since 1.1.11), QSynth, Polyphone etc.

[trebmuh]

👍
Adding LMMS and Carla to the list.