Handle project.godot files

[JoNax97]

Add the posibility to open .godot files, so that users can associate this file type with gvm.

In my oppinion, it should behave as follows:

• If a matching Godot version is installed, launch Godot directly to the project, skipping both gvm and Godot's project window.
• Else, open gvm and prompt the user to either install the required version or choose other version.

Edit: I'd be willing to try and implement this feature if you're OK with this.

[noidexe]

I'm planning on a full rewrite so it's probably better to add it then. How did you plan to implement it? project.godot before 4.0 doesn't tell you the exact version that should be used. Also, gvm doesn't really now which versions are installed, it only has a list of paths and arguments (that will change in 2.0). You can currently drag and drop a .godot file and it'll pop up the Add version window. The whole idea behind a project/version manager is that you don't have to go to each project folder every time you want to open it so I'm not sure how many people would need that workflow.

I'll leave the open for discussion in case anyone else wants to share their thoughts.

[Kregap]

Personally I downloaded some repositories from Godot Engine and GDQuest, so it would be nice to either scan directory with multiple projects in subdirectories or open project from godot.project file as @JoNax97 suggested, flow mentioned by him is nice too. Additionally you might want to open project from file already matched in GVM as an added project beforehand.