Downgrading a package with dotnet add package --version is silent #56

Summary

When the CLI adds a NuGet dependency (for example Blazor-ApexCharts for charts) with dotnet add package X --version <v>, and the project already references a higher version of X, the reference is silently downgraded.

Expected

Keep the higher version (and say so), or ask before downgrading.

Suggested fix

Read the existing PackageReference before calling dotnet add package, and skip the call when the installed version is equal or higher. Add a test with a project that already references a newer version.