add lts note to README
add lts note to README

NebulousLabs/Sia,mtlynch/Sia,MrStrong/Sia,mtlynch/Sia,MrStrong/Sia,ericflo/Sia,mnsl/Sia,ChrisSchinnerl/Sia,ericflo/Sia,mnsl/Sia,mharkus/Sia,mharkus/Sia,NebulousLabs/Sia,ChrisSchinnerl/Sia