Added SmartCharging documentation to README

[folkengine]

Describe your changes

Updated README.ms adding documentation specifically for our work with SmartCharging. I still feel like there could be a lot more done and I'm looking for suggestions.

Tasks:

• Cleaned up markdown issues in the README as a whole.
• Consolidated portions of the text that were only for 1.6 that can apply the the library in general.
• Added sections for the SmartCharging work adding sequence diagrams of the flow.

Issue ticket number and link

https://github.com/US-JOET/base-camp/issues/184

Checklist before requesting a review

• [✅] I have performed a self-review of my code
• [✅] I have made corresponding changes to the documentation
• [❎] If OCPP 2.0.1: I have updated the OCPP 2.0.1 status document
• [✅] I read the contribution documentation and made sure that my changes meet its requirements

[folkengine]

@gberardi-pillar I'm thinking it would be good to add some stuff about your constructor update.