fix: add OS check to pdeathsig

[Davincible]

Fix Windows/ Mac support

On linux with pdeathsig it will automatically kill the child processes, that is currently not implemented on mac/linux

[mihaiav]

@Davincible that's not working on MacOS for obvious reasons. You can try to build for MacOS using the GOOS=darwin and GOARCH=amd64 and still get the error.
I believe using build tags like in my PR is the idiomatic way to support different platforms. As Go is a compiled language you cannot reference platform specific code (i.e. *syscall.SysProcAttr) and ignore it at runtime. You have to use build tags. It's the only way.

Even if that code would somehow compile(it's impossible) you still try to create a frame buffer (newFrameBuffer) that will fail on both MacOS and Windows because none of them support Xvfb.

env GOOS=darwin GOARCH=amd64 go build

./chrome.go:158:22: cmd.SysProcAttr.Pdeathsig undefined (type *syscall.SysProcAttr has no field or method Pdeathsig)
./display.go:83:20: xvfb.SysProcAttr.Pdeathsig undefined (type *syscall.SysProcAttr has no field or method Pdeathsig)

[yms2772]

Unless specify a build tag, Windows or MacOS will read that code unconditionally, and inevitably, errors occur.