Docs: Make Clear That Go 1.20 is Expected

[jspeed-meyers]

Description

When I cloned and then installed wolfictl, I ran into an error because, I think, the go version on my machine was 1.19, less than 1.20. Is this expected? If so, should the README note that the Go version is expected to be 1.20? Apologies if this is an inane question. I don't consider myself competent in Go.

I ran this:

➜  public git clone git@github.com:wolfi-dev/wolfictl.git wolfictl && cd $_

Then this:

➜  wolfictl git:(main) go install`
...
go: downloading modernc.org/memory v1.5.0
go: downloading github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec
# github.com/chainguard-dev/go-apk/pkg/apk
../../../../go/pkg/mod/github.com/chainguard-dev/go-apk@v0.0.0-20230710230135-7fc46e8b3c4d/pkg/apk/expandapk.go:89:16: undefined: errors.Join
note: module requires Go 1.20

note: module requires Go 1.20 seemed to indicate that I needed Go 1.20, at least.