[innosetup] Support importing folder from File Explorer menu

[victoryforce]

This PR adds "import to darktable" entry to the File Explorer right-click menu on a folder.

[victoryforce]

@TurboGit - As always, it's better to ship improvements to the innosetup-based installer as early as possible for more testing by early testers of development snapshots...

[TurboGit]

@victoryforce : Would this affect the 5.4.1 bug-fix release?

[victoryforce]

@victoryforce : Would this affect the 5.4.1 bug-fix release?

This will only affect the 5.4.1 release if we decide to build it for Windows using this new installer, otherwise, it has no effect on 5.4.1.

This PR adds a new feature, the ability to import a folder by selecting an item in the menu that opens when you right-click on a folder in File Explorer. Although this is a new feature and not a fix, there is no potential for this to be a BIC ("bug-introducing change"), as all that is changed is that it adds an instruction for File Explorer to launch darktable with the folder name on the command line when selecting the menu item. And of course, I tested that it works.

[TurboGit]

Ok, let's merge this and use @wpferguson Windows build for 5.4.1. As discussed we will move to InnoSetup from GitLab-CI on 5.6.