[Documentation] Document the different flows & modes of PATH operation

[Olshansk]

Objective

Make it clear and easy to understand the intersection of web2/web3 when interfacing with POKT/PATH.

Origin Document

• The notion document titled Different Modes of Operation (PATH)
  

• See this page in the poktroll docs as another reference:
  

Goals

• Set the foundation for "Gateway Abstraction" documentation
• Clearly identify all the different modes that users need support for in the short and long term
• Identify technical gaps (if they exist) in the implementation and/or design

Deliverables

• A new page in https://path.grove.city/ titled Gateway Abstraction
• Identify, add or remove missing user flows from the list above
• Mermaid diagrams for each flow above
• Written details for each flow above

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Creator: @Olshansk
Co-Owners: @adshmh @red-0ne