Set LicenceExpression for package

[thompson-tomo]

Is your feature request related to a problem? Please describe.
In dependency track this package is reporting as not having a licence type specified

Describe the solution you'd like
The PackageLicenseExpression property is set in the csproj so thay the NUGET package has the information. This can then ben included in the SBOM so that analysis can occur in the appropriate tools

Describe alternatives you've considered
Ignore them, bundle licence file into package & reference the file.

Additional context
As per https://learn.microsoft.com/en-us/nuget/reference/msbuild-targets#pack-target, PackageLicenseUrl is deprecated