fix: Use references to renderers instead of inline functions

[kizu]

In order to be able to check if a column has a default renderer, we need them to be exposed constants instead of inline functions.

This way we could do, say:

import { emptyRenderer } from 'react-table';
// …
if (column.Header === emptyRenderer) {
  // …
}

Right now these are inline functions that cannot be compared with anything, so having publicly available references to these could help a lot when developing plugin-hooks that work with columns.

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[tannerlinsley]

🎉 This PR is included in version 7.3.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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[nextglabs]

Very nice, but this seems like the emptyRenderer function is missing from the Typescript types (tested with @types/[email protected])