Link to detailed docs over at docs.entropy.xyz

[mixmix]

This was a checklist item from a PR that didn't get done:

• make sure the SDK README gets a link to the detailed docs.

[johnnymatthews]

In a call with @frankiebee the other week, we discussed that there aren't many relevant links to docs.entropy.xyz that we need to add into this repos README, other than to the docs homepage. Relevant content is coming, but it's not availabel as of yet.

We can keep this issue open until there are relevant pages within the docs that would be useful to link to. Or we can close this and recreate a similar issue to this one the content is available. I'll leave it up you @mixmix to decide whether to close this now or not.