Improved overview of Playnite Web parts

[andrew-codes]

Issue #850 has uncovered that the documnetation surrounding both how to install and setup Playnite Web and communicting the fundamental parts of how it works needs improvement. This issue tracks improvements to the overall components and how they work together to create Playnite Web.

Note that is #853 is released prior to this work being done, we can also include the Playnite Web MQTT plugin as a part of the system.