Use collapsable markdown on Readme's Currency List

[radiovisual]

The currency list is growing fast! It is nearly 4,000 items long 😱 so it takes forever to view.

An idea could be that when the currency list is generated, (since the Readme is auto-generated when we run npm run build, it could also sort the list of currencies, and instead of just printing out a full table of currencies, it breaks up the sorted currencies with some collapsable markdown and make a list like this:

0-9

Table with 0-9 currencies here

A

Table of currencies starting with 'A' here

B

Table of currencies starting with 'B' here