[Breaking Changes] Fix FrameShow enum

[reduckted]

🚨 This contains breaking changes 🚨

A few improvements to the FrameShow enum. Hopefully the breaking changes won't actually affect anyone. 🤞

1. It was marked with the [Flags] attribute. The underlying __FRAMESHOW enum is not flagged.

2. There was a redundant Unknown member with a value of zero. That is equivalent to both FRAMESHOW_Hidden and FRAMESHOW_WinHidden. I've removed Unknown. This is a breaking change.

3. FRAMESHOW_Hidden is documented as being obsolete and has the same value as FRAMESHOW_WinHidden. I've removed WinHidden rather than Hidden because there is no corresponding WinShown value (but there is a Shown value). This is a breaking change.

4. I've added enum values for __FRAMESHOW2, __FRAMESHOW3 and __FRAMESHOW4.

5. I've added a comment to the <summary> tag that specifies the underlying enum value. When I was trying to understand which value I should be using, I found myself searching the web for examples. First I had to discover the Visual Studio enum that FrameShow is actually wrapping, and then find the corresponding enum member name. It would have been much easier if it was all available in the documentation comments.

ℹ️ One thing about the documentation comments that I noticed - when the enum is used within the same solution as the toolkit, intellisense actually shows the value assigned to the enum, like so:

But when you're referencing the actual NuGet packages, intellisense only tells you the numeric value:

Hence why I've added the underlying enum member to the documentation. 😄

[madskristensen]

Awesome. Thank you so much!