Fixes #39: Adds a shell extension to list installed IDLE on .py files

[zooba]

This likely needs more work to be robust, and we might need/want to bring over the implementation from the previous shell extension to handle drag-drop as well (or it may just be fixed with the MSIX install). But getting it up as a starting point!

[Copilot]

Pull Request Overview

This PR adds a new shell extension project configuration to list installed IDLEs on .py files. Key changes include:

• Introducing a new CProject configuration for "pyshellext" with VersionInfo, build ItemDefinitions, and associated source/resource files.
• Configuring linker settings and module definition file for the shell extension.

Files not reviewed (5)

• src/pymanager/appxmanifest.xml: Language not supported
• src/pymanager/msi.wxs: Language not supported
• src/pyshellext/default.manifest: Language not supported
• src/pyshellext/pyshellext.def: Language not supported
• src/pyshellext/pyshellext.rc: Language not supported

[zooba]

Unsurprisingly, Copilot didn't have anything helpful to add :)

I'm a little hesitant to ship this, as I do think it needs more testing. Unfortunately, without it being part of the install, it's impossible to test. So I think we just need to bite the bullet, bring it in, and be ready to respond if it breaks.

Best way to disable it is to search your registry for C7E29CB0-9691-4DE8-B72B-6719DDC0B4A1, find the ExplorerCommandHandler value containing the UUID (there'll be some other mentions that are fine) and delete it. It shouldn't come back until the next update, but I'm not 100% on that. (Or change your .py association by doing "Open With" and choosing something else "Always".)

[zooba]

Have confirmed that it works on ARM64 when recompiled for ARM64, but we're not doing platform-specific releases yet. That'll be a new feature.

Once this passes CI, I'm going to merge it.