modvendor command

Modvendor is an internal utility to reset the vendor content using "go mod vendor" and to copy the glfw c source code dep. The last action is required since "go mod vendor" do not handle directories not containing a .go file inside (see https://github.com/golang/go/wiki/Modules#some-needed-files-may-not-be-present-in-populated-vendor-directory).

Usage:

go run scripts/modvendor/main.go

Note: modvendor must be executed from the fyne project root