Document type converters available for parameters

Right now, we support a few different ways things can be converted into a parameter. However, we don't tell this to the user... in any way. So, they don't know what we don't tell them. We would need to add an attribute onto the generated cmdlets that says what input types via type conversion are allowed. Then, the documentation generator can render that into the Parameters section of the markdown document. I don't know if this would get displayed in the Get-Help.