TruthClassification - minor updates on the classification scheme and modification of README
Deleted the PromptLike Category purposed in previous MR. We relied on the matched parent of the muon, in this category, a W-boson, to perform this classification originally. However, It was found that a W-boson could undergo leptonic or hadronic decays, and therefore the PromptLike category could be misleading.
Also, flowcharts of the classification scheme for both electron and muon are attached in README to offer a brief introduction to the users.