[alias-server] Update README in line with current API endpoints

Summary: Update README to reflect latest state of alias-server endpoints

Test Plan: Review for consistency, check endpoints at alias.etokens.cash/ base

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D14559