docs: Update charts documentation
docs: Update charts documentation

Add a note about charts in general and details about TMS and MBTiles
SignalK/signalk-server-node,SignalK/signalk-server-node,webmasterkai/signalk-server-node,webmasterkai/signalk-server-node,webmasterkai/signalk-server-node,sbender9/signalk-server-node,sbender9/signalk-server-node,sbender9/signalk-server-node,SignalK/signalk-server-node,SignalK/signalk-server-node