[docs] List all existing API functionality in markdown

[dignifiedquire]

• level 2 - cli
• level 2 - http see Spec out current state of the http api #7

[RichardLitt]

These are now all documented in #13, and the level documentation has moved to https://github.com/ipfs/specs/tree/master/api. Ought we to close this, or reopen it in ipfs/specs, where we would need to fill out the CLI and HTTP docs for transport-specific methods?

[daviddias]

As pointed on ipfs/kubo#2165, go-ipfs HTTP API is accepting all methods in all endpoints, this creates space for some security holes (doing operations on GET that can bypass CORS protection.

[daviddias]

for reference:

• core (programmatic interface) - https://github.com/ipfs/specs/pull/65/files
• http-api - inside this repo
• cli - https://github.com/ipfs/specs/pull/65/files

[RichardLitt]

I think we can close this, @diasdavid. I don't see that the original purpose is needed anymore.