Refine pandoc build workflow using build script

We should unify the build workflow in CI and VS Code using a build script to make it more consistent. Most importantly, when going the markdown way, we need to concatenate files beforehand for pandoc-crossref to work correctly (cross references across multiple files cause issues). When generating a temporary concatenate, we need to add that to .gitignore.

Build Script

#!/bin/bash

# cleanup
latexmk -C
if [ -f chapter/out.tex ]
then
    rm chapter/out.md
    rm chapter/out.tex
fi

# run pandoc
if [ $1 == "pandoc" ]
then
    cat chapter/*.md > chapter/out.md
    pandoc --filter pandoc-citeproc --filter pandoc-crossref \
        -M cref=true --top-level-division=chapter \
        --bibliography library/library.bib --biblatex \
        -o chapter/out.tex chapter/out.md
fi

# run latex build
latexmk -latexoption="-shell-escape" main.tex