Feature request: read `minimum_zig_version` field of build.zig.zon

[jeffective]

Thanks for making this awesome tool! I love how simple it is to install and use.

What do you think about a feature like this?

1. when zigup is run within a folder that contains a build.zig.zon, zigup will install the version of the compiler specified by the minimum_zig_version field.

if running zigup with no arguments does too much in this case, then perhaps it could be:

• zigup zon
• zigup here
• zigup this
• zigup cwd

[marler8997]

Seems like a reasonable enhancement. You might be interested in my new project https://github.com/marler8997/anyzig which uses this mechanism but does so with a new zig executable (a little bit different then your proposal).