.latexmkrc generation for LaTeX Workshop

[tueda]

Because typesetting in LaTeX Workshop is basically based on latexmk, we could add a target that generates .latexmkrc containing exec "make"; in such a way that the default recipe of LaTeX Workshop does the job for our Makefile.

We could also output dummy messages (Latexmk: applying rule 'latex') in typesetting in order to make LaTeX Workshop's log parser work it out:
https://github.com/James-Yu/LaTeX-Workshop/blob/9da83fc4cd7ef18949a8120d958a9e2d70f704d8/src/components/parser/compilerlog.ts#L41