Integrate automated builds into HDRMerge GitHub project

[Carmelo_DrRaw]

@Morgan_Hardwood

@Carmelo_DrRaw you did a great job integrating automated Windows (and AppImage) builds of RawTherapee , could the same be done for HDRMerge?

The HDRMerge AppImages are already built and deployed via Travis CI: Release Automated Builds · jcelaya/hdrmerge · GitHub

So far I have not done any attempt at building a Windows version…