port zero-cost-rescript example

[ryyppy]

There are some breaking changes when porting over https://github.com/bobzhang/zero-cost-rescript from reason-react.

Good data points for some legacy api usage (also good for writing migration guide).

[bobzhang]

done in that repo. Edit: reopened in case you need update some docs

[cknitt]

Closing this issue, as it is about the past transition from reason-react to @rescript/react that happened 1 1/2 years ago.