Add Loan Type info in README
Add Loan Type info in README

   Loan types info:
   `APR <https://en.wikipedia.org/wiki/Annual_percentage_rate>`_,
   `EAR <https://en.wikipedia.org/wiki/Effective_interest_rate>`_,
   `Real Rate <https://en.wikipedia.org/wiki/Real_interest_rate>`_.

cc @etobella
ddico/account-financial-tools,ddico/account-financial-tools