Templates / CI: Install or warn about missing packages

[ArchibaldBienetre]

Noticed in #17: not all packages we want may be aboard initially.

We must guarantee the needed ones are installed.

How to install: https://www.tug.org/texlive/pkginstall.html

• Verify that the tlmgr command is installed, like we already verify pdfunite, tex and others
• Create convenience method in ShellUtil to call package installer
• Create install routine that installs missing packages idempotently
• As usual, test this

See #17 for a file we can use in tests + for a list of which packages we may need:

\usepackage[english, german]{babel}
\usepackage[top=40mm, headheight=4cm, bottom=55mm,left=3cm,right=2cm]{geometry}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{array}
\usepackage{tabularx,ragged2e,booktabs}
\usepackage{enumitem}
\usepackage{hyphenat}
\usepackage[bottom]{footmisc}
\usepackage{fancyhdr}
\usepackage{helvet}
\usepackage[hidelinks]{hyperref}
\usepackage{cleveref}
\usepackage[dvipsnames]{xcolor}
\usepackage{fontawesome5}
\usepackage{pgf}
\usepackage{pgfpages}
\usepackage{marvosym}

[ArchibaldBienetre]

Consulting @DonMischo on this issue I'm facing...

$ tlmgr install geometry
(running on Debian, switching to user mode!)
(see /usr/share/doc/texlive-base/README.tlmgr-on-Debian.md)
TLPDB: not a directory, not loading: /home/hoobert/texmf
tlmgr: user mode not initialized, please read the documentation!

[ArchibaldBienetre]

:information_source: I can add a simple test by having the wrong package installed (texlive), and the right package installed (texlive-full), then running against a nearly-usepackage-only tex file.

[ArchibaldBienetre]

Pull request: https://github.com/SergelsOrg/csv2tex/pull/73