Easily compile latex documents with nix flakes.

Some implementation that can perform similar functions: tex2nix, latex-tools, If you are not happy with my implementation, or want to try other similar features, please feel free.

nix flake init --template github:jackyliu16/latex-utils

• provide more information and a help panel for easily debug
• provide support of multiple compilations like xelatex -> bibtex -> xelatex -> xelatex Right now we could finish this job with override buildPhase like xelatex main.tex; bibtex main.aux; xelatex main.tex, should we provide latexmk as default ? it look fine for me to replace this kind of operation.
• Fixed identification of RequirePackage
• Due to regular expression limitations, cross-line RequirePackage and usepackage cannot now be detected, need to manually convert it into one line .

\RequirePackage[
a4paper,
left=3cm,right=2.3cm,top=2.3cm,bottom=2.6cm,
headheight=10cm,
headsep=0.3cm]{geometry}

• Right now, there is inputFile required, if the default operation doesn't belong to latex_utils, it seems reasonless to provide this kind of variable, never mention the chance may use it right here (overlays buildPhase and installPhase in flakes).
• Maybe we should base on latexmk, latex-tools impl watch operation, should we just simpliy abstract the document, and provide diff kinds of package of build or watch or just make up this kind of operation in devShells.