chainntfns: document the ChainNotifier interface
chainntfns: document the ChainNotifier interface

aakselrod/lnd,BitfuryLightning/lnd,bryanvu/lnd,LightningNetwork/lnd,LightningNetwork/lnd,ddustin/lnd,aakselrod/lnd,ddustin/lnd,bryanvu/lnd,BitfuryLightning/lnd,AndrewSamokhvalov/lnd,AndrewSamokhvalov/lnd