Add support for 'Static'

[Stephanevg]

Static methods / properties should be underlined in the diagram.

See example here --> https://dfinke.github.io/powershell,%20design%20patterns/2018/04/13/PowerShell-And-Design-Patterns.html

[Stephanevg]

Find how to underline in psgraph. Update Write-CuClassdiagram