Nano 12 - make the library ESM-only. Exchange all "require"s for "import"s.

[glynnbird]

Overview

Preparation work for Nano 12.

• Making the library ESM-only - remove any "require" use and replace with equivalent "import".
• version 12.
• Update README code to eliminate "require".
• Remove a bunch of legacy Nano code that dates back to the request/axios days. It's a bit simpler to read now with the "relax" method making the request and handling the response.
• The ..AsStream variants of the functions are now "async" - i.e. they return a Promise which resolves to a stream, rather than synchronously returning a dummy stream as before. This makes the code easier to maintain, but is a breaking change.

Testing recommendations

All the tests have changed in the require-->import sense, but are functionally identical.

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes;

[glynnbird]

Note to future self: It is possible to turn the ESM into CJS with:

rolldown --input lib/nano.js --file lib/dist.js --format cjs

I think ESM is the future though