[docs] Umbrella issue for v3 docs

[gadicc]

Docs are the biggest blocker for v3 becoming "official". Let's track all oustanding issues.

[gadicc]

Part of the v3 docs involve moving from docs/*.md to inline JSdocs wherever possible. This is a lot more maintainable, and since we publish to jsr.io now too, we also get a free html build of the docs, e.g. https://jsr.io/@gadicc/yahoo-finance2/doc/~/default. It also makes using the library with a good editor much more useful too. It will be great as we gradually keep improving the inline jsdocs moving forward.