Adds Gaffer support

[sosoyan]

Changelog Description

Added support for Gaffer and should work with ayon-gaffer addon
https://github.com/RVXStudio/ayon-gaffer

Additional review information

https://github.com/GafferHQ/gaffer

Testing notes:

1. Add a path to your gaffer executable in Application Settings
2. Run as any other application from Launcher

[BigRoy]

Looks good to me - I think it'd be nice to add default paths for windows and linux as pointed out in my comment because it'd aid admins to know what to point to.

Other than that, this is indeed what is needed to add gaffer app support.

Might be nice in the PR description to point to a matching ayon-gaffer integration addon repository that may work with this PR - just so it's tracked here for the future.

E.g. I know of https://github.com/RVXStudio/ayon-gaffer

[MustafaJafar]

It works.
Because there's no addon for it I think AYON will only launch it.

[sosoyan]

It works. Because there's no addon for it I think AYON will only launch it.

I'm working on minimal ayon-gaffer addon will pr when it's ready.

[sosoyan]

I'm working on minimal ayon-gaffer addon will pr when it's ready.

I've pushed a minimal host addon now
https://github.com/sosoyan/ayon-gaffer