[gatsby-link] to should be of type string or location object

[nsimonson]

Description

gatsby-link does not accept a location object as specified in react-router as a valid prop.

Environment

Gatsby version: 1.9.119
Node.js version: 8.9.1
Operating System: macOS 10.13.2

Actual result

<Link to={{ pathname: '/my-page', search: '?sort=name', }} />

Passing an object to the to prop of Link results in a url of "/[object Object]"

Expected behavior

Url should be "/my-page?sort=name"

...

Current work around is to use Link directly from react-router-dom

[KyleAMathews]

Yeah, we don't currently support the location version — for no particular reason :-) Happy to take a PR to gatsby-link adding support!