[MPL] Added the parameter documentation for CapillaryPressureRegularizedVanGenuchten

Documentation/ProjectFile/properties/property/CapillaryPressureRegularizedVanGenuchten/c_CapillaryPressureRegularizedVanGenuchten.md

+\copydoc MaterialPropertyLib::CapillaryPressureRegularizedVanGenuchten

Documentation/ProjectFile/properties/property/CapillaryPressureRegularizedVanGenuchten/t_exponent.md

+\copydoc MaterialPropertyLib::CapillaryPressureRegularizedVanGenuchten::m_

Documentation/ProjectFile/properties/property/CapillaryPressureRegularizedVanGenuchten/t_p_b.md

+\copydoc MaterialPropertyLib::CapillaryPressureRegularizedVanGenuchten::p_b_

Documentation/ProjectFile/properties/property/CapillaryPressureRegularizedVanGenuchten/t_residual_gas_saturation.md

+\copydoc MaterialPropertyLib::CapillaryPressureRegularizedVanGenuchten::Sg_r_

Documentation/ProjectFile/properties/property/CapillaryPressureRegularizedVanGenuchten/t_residual_liquid_saturation.md

+Residual saturation of liquid phase.