Document the [@react.component {props}] payload

[yawaramin]

Currently it's not documented that the attribute can take a props payload that sets the name of the component prop in JS output. E.g., [@react.component {props: myProps}] will output JS: function Component(myProps) {...}.

Seems like a good place to add this would be the [@react.component] section of the doc page: https://reasonml.github.io/reason-react/docs/en/components#reactcomponent