go.dev: make links to examples automatically unfold example

[kortschak]

What is the URL of the page with the issue?

https://pkg.go.dev/github.com/twpayne/go-vfs/vfst?tab=doc#example-NewTestFS

What is your user agent?

Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:75.0) Gecko/20100101 Firefox/75.0

Screenshot

What did you do?

Navigate to https://pkg.go.dev/github.com/twpayne/go-vfs/vfst?tab=doc#example-NewTestFS and expect to see that the example is unfolded as it is in the case of documentation examples on golang.org like this https://tip.golang.org/pkg/fmt/#example_Errorf, but see that it isn't.

What did you expect to see?

Unfolded examples.

What did you see instead?

Folded example.

[julieqiu]

Thanks for the feedback! Adding this to #37819.

[dmitshur]

Is this issue different from #37520?

[kortschak]

No. This is a duplicate. Thanks.