Update plgx prerequisites

[dannoe]

KeeTrayTOTP/KeeTrayTOTP/KeeTrayTOTP.csproj

Line 12 in 650364b

<DotNetVersion>3.5</DotNetVersion>

We have to increment this to 4.5. We use several things that are not included in the .NET Framework
3.5. Used for displaying a nicer error message to the user, if the required .net framework is not installed at plgx compilation time.
see Plugin Development (2.x) - KeePass

[Sanaki]

This may break mono builds. While I don't know the reason, mono seems to internally report an old version of .net despite being much more up to date.
Another project's fix when encountering this issue: dlech/KeeAgent@c09f3dd

EDIT:

For compatibility reasons, Mono’s System.Environment.Version property returns the version of the .NET profile that Mono targets, not the version of Mono that is being used. This should be the same version number that .NET would return. As such, it will return 2.0.X.Y when running under the 2.0 profile, even though it’s running under Mono 1.1. :-)
Source

So yeah, I'm not sure what's going on there. Seems like that shouldn't be an issue.

[robinvanpoppel]

That 3.5 feels wrong indeed. This is an area that I have not really explored myself. Would it be possible to bump to 4 at least? And maybe we can add specific github actions that build and test the plugin against mono to ensure compatiblity?