Allow built-in components in render prop

[tricoder42]

Just a small nitpick.

It's possible to use React.Component to render translation: <Trans render={Component}>...</Trans>, but built-ins can be passed as elements only: <Trans render={<h1 />}>...</Trans>.

Proposal: <Trans render="h1">...</Trans>

It's like 4 chars difference, but nice to have 😸