docs need details on AccountUpdate, actions, and events number limits within a tx

[barriebyron]

docs will benefit from more details on AccountUpdate/actions/events number limits within a tx.

this knowledge gap was reported in MF Cohort 1 Technical Feedback see ROW 4

improve more details on TokenAccount section, such as some demo cases, why we have both signature auth and proof auth

SnarkyJS features used zkProgram, SmartContract, fetchActions, fetchEvents, AccountUpdate, MinaSigner, LocalBlockchain, etc.