Support linking to individual methods

Before API spec was in wiki and it was possible to reference with anchor, e.g.
https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_newfilter
to link directly to `eth_newfilter` point

Now spec URL is mouthful
https://playground.open-rpc.org/?schemaUrl=https://raw.githubusercontent.com/ethereum/eth1.0-apis/assembled-spec/openrpc.json&uiSchema%5BappBar%5D%5Bui:splitView%5D=false&uiSchema%5BappBar%5D%5Bui:input%5D=false&uiSchema%5BappBar%5D%5Bui:examplesDropdown%5D=false
and it is not possible to get link to specific JSON-RPC method.