[ecash-lib] Fixed Typo and added ALL_BIP143 to imports on README
Summary: Changed "inputs" to "input" and added ALL_BIP143 to import
Test Plan: check out modules/ecash-lib/README.md
Reviewers: #bitcoin_abc, bytesofman
Reviewed By: #bitcoin_abc, bytesofman
Differential Revision: https://reviews.bitcoinabc.org/D16943