Chain-specific docs

Aside from generic documentation for polkadot-api, we also provide generated documentation for well-known chains, based on the metadata.
With these, you can search for apis like limited_teleport_assets, their type parameters, and the docs that metadata provide for them.

You can also generate the same documentation for any chain, using papi-generate-docs binary, provided by @polkadot-api/docgen package:

npm install polkadot-api @polkadot-api/docgen
papi add <...>
papi-generate-docs --config <path-to-papi-config> --output <docs_directory>