Support for calling vugufmt

[bradleypeabody]

I think if vugufmt were to only handle extracting the Go script portion of a .vugu file and running gofmt and/or goimports on it, and then this extension called vugufmt upon save by default - that behavior would be really useful for people.

HTML formatting is nice, but Go formatting is probably more immediately useful, and it's easier to solve.

I can do the needed changes to vugufmt to make this happen. Do you think you'd be able to add the ability to install vugufmt automatically (just using go get and/or go install) when your extension is first loaded and then calling vugufmt automatically upon save? (Probably an option for this would be appropriate so it can be disabled if needed.)

[bradleypeabody]

Hm, actually I'm just now seeing that this is not the extension that shows up with VSCode's Install Extension option - but let me know anyway if you're interested in collaborating.