Bug: README hyperlinks no longer valid

[cep21]

Hi,

The README file inputs section links to https://github.com/docker/buildx#--cache-tonametypetypekeyvalue (Along with others on buildx)

This is no longer an anchor link on that page. Is there another page the README should link to for

[crazy-max]

Hi @cep21,

This is no longer an anchor link on that page.

Yes, we need to update these links (docker/buildx#571 (comment)).

Is there another page the README should link to for

https://github.com/docker/buildx/blob/master/docs/reference/buildx_build.md