format: decl group allow first comment

[Oiyoo]

fixes #212

[mvdan]

What if the comment was actually a directive, like:

//go:embed hello.txt
var embedded string
var foo int
var bar float

Presumably this would break the directive, but I haven't checked:

//go:embed hello.txt
var (
    embedded string
    foo int
    bar float
)

[Oiyoo]

What if the comment was actually a directive, like:

//go:embed hello.txt
var embedded string
var foo int
var bar float

Presumably this would break the directive, but I haven't checked:

//go:embed hello.txt
var (
    embedded string
    foo int
    bar float
)

thanks, PTAL

[mvdan]

Tests SGTM, just some thoughts about the code

[mvdan]

Thanks!