validate and update vendor

[crazy-max]

Adds sandboxed vendor update and validation in the Dockerfile. A bake definition has been created to ease the integration as well as a GitHub Actions job.

As follow-up we could look at sandboxing the build process with cross compilation.

[rcjsuen]

@crazy-max Thanks for this!

Could you update README.md with some instructions clarifying what is being performed to achieve some desired result? So instead of running make tidy someone should run make vendor?

[crazy-max]

Could you update README.md with some instructions clarifying what is being performed to achieve some desired result? So instead of running make tidy someone should run make vendor?

Sure let me do this

[crazy-max]

Could you update README.md with some instructions clarifying what is being performed to achieve some desired result? So instead of running make tidy someone should run make vendor?

Sure let me do this

Added this to contributing docs similar to https://github.com/docker/buildx/blob/1e50e8ddabe108f009b9925e13a321d7c8f99f26/.github/CONTRIBUTING.md?plain=1#L171-L189