Add package-level descriptions in Go docs (plus general approach to auto-generated docs)

[Mr0grog]

Some of the Go packages we generate documentation for don’t have comments describing the package as a whole. Others have them, but they’re extremely minimal. We should have good, rich descriptions with examples for all of them.

Each should contain a clear description of the package, information about how it relates to other packages, any notes about stability (how experimental/subject to change is it?), and at least one small example of basic usage (options might be an exception because it’s just defining types…?).

Relevant packages:

• core/coreapi (no overview) Add package overview comments to coreapi ipfs/kubo#5108
• core/coreapi/interface (one sentence)
• core/coreapi/interface/options (no overview)
• go-ipfs-api (one sentence)

See also this comment on #68.

[jessicaschilling]

Auto-generated Go docs are being generated somewhat differently now -- but we still need to address best approach to this as part of the new docs beta.