Add support for the \includestandalone command, providing autocomplet…

[slideclimb]

…ion and file referencing, fixes #3844

Fix #3844

Summary of additions and changes

• Add support for the \includestandalone command, providing autocompletion and file referencing

How to test this pull request

main.tex

\documentclass{article}
\usepackage{standalone}

\begin{document}
    test
    \includestandalone[mode=buildmissing]{image}
\end{document}

image.tex

\documentclass[10pt,border=3mm]{standalone}
\usepackage{tikz}

\begin{document}
    \begin{tikzpicture}
        \draw (0,0) -- (0,5);
    \end{tikzpicture}
\end{document}

• Updated the documentation, or no update necessary
• Added tests, or no tests necessary