Add example on fixed trapping time to manual

trapping_function_holes = "1/([0]*pow([1]/263,[2]))/[3]"

trapping_parameters_holes = 7.7e-16cm*cm/ns, 293K, -1.52, 1e14/cm/cm

\end{minted}

Fixed, effective trapping times can be defined using this model similar to the following configuration example.

\begin{minted}[frame=single,framesep=3pt,breaklines=true,tabsize=2,linenos]{ini}

# Defining a fixed trapping time

trapping_model = "custom"

trapping_function_electrons = "[0]"

trapping_parameters_electrons = 5ns

trapping_function_holes = "[0]"

trapping_parameters_holes = 7ns

\end{minted}