New CV Template: Plain CV

[amarz45]

Plain CV is a new CV template that I created to basically make a more plain version of Awesome CV. Awesome CV is really nice but some people prefer having a plain résumé. The three main differences are:

1. Plain CV uses pdflatex instead of xelatex. This is to decrease compile time and since the default font is just plain Latin Modern (lmodern).
2. PlainCV does not use the \fontsize command. It instead specifies sizes like \large, \Huge, etc. This makes more sense to me.
3. PlainCV only uses the color black.

[mitchelloharawild]

Thanks for the PR, and apologies for not reviewing this sooner.

To reduce the maintenance needs for the package, I can only accept templates which are substantially different in appearance from other templates. I'm currently working on a quarto variant of vitae, which will make it (1) easier to create new templates and (2) easier to maintain many new template options.

As such, I am closing this PR as I don't think it is a good fit for the vitae R package. I do however believe that it is a great match for the upcoming collection of vitae quarto extensions.