Improve Readme.md

[tukkek]

• [ ] When rendered on Github, the file is being shown in only one line (you either have to use Markdown syntax or rename the file to Readme.txt for it to be rendered like text)
• [ ] How can modders access the XP values the player has? How can a mod subtract "spent" XP?
• [ ] Have a full example of a configuration file (either in the Readme with markdown syntax or in a separate file as an example). The current Readme alone isn't clear how the configuration file must be handled (what does "foreach node" means, for example)?