\documentclass{l3doc}
\usepackage[T1]{fontenc}
\usepackage{pdfpages}
\usepackage{standalone}
\providecommand{\defopt}[1]{\underline{#1}}
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\begin{document}
\section{Package implementation for developers}
\EnableDocumentation
\DisableImplementation
\DocInput{gotham.dtx}
\end{document}