Add more examples using curl to the README

[mhfowler]

based on a discussion with @moid on ssb %/q6q4t3WMS7dVVKErsjvOTInR2ZGvMZb5yAiKrl0Ecg=.sha256

it looks like maybe the one example of curl we could find in the documentation was out of sync,
and in addition to the jsonrpc examples in rust for solar_client,

it could be nice to provide examples in curl, as a reference for those interacting with solar from the command line of from another language

[mhfowler]

e.g.

whoami:

curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc": "2.0", "method": "whoami", "id":1 }' 127.0.0.1:3030

publish:

curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc": "2.0", "method": "publish", "params": {"msg": {"type":  "post", "text": "this is a test post for moid"} }, "id":1 }' 127.0.0.1:3030

feed (of the ID returned by whoami in my case):

curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc": "2.0", "method": "feed", "params": {"pub_key": "@3TOzePzvEXgEDf7/jKmpDjlTHRs1e98GDzfIItAQHM0=.ed25519" }, "id":1 }' 127.0.0.1:3030