Replace deprecated Docker base image with the suggested alternative

[ndsvw]

The base image of the Dockerfile (pandoc/alpine-latex) is deprecated and should be replaced with "pandoc/latex" (as suggested here)

I tried it out, but it seems that further changes are required:

markdown-cv-mdcv-pdf-1   | Error producing PDF.
markdown-cv-mdcv-pdf-1   | ! LaTeX Error: File `xltxtra.sty' not found.
markdown-cv-mdcv-pdf-1   | 
markdown-cv-mdcv-pdf-1   | Type X to quit or <RETURN> to proceed,
markdown-cv-mdcv-pdf-1   | or enter new name. (Default extension: sty)
markdown-cv-mdcv-pdf-1   | 
markdown-cv-mdcv-pdf-1   | Enter file name: 
markdown-cv-mdcv-pdf-1   | ! Emergency stop.
markdown-cv-mdcv-pdf-1   | <read *> 
markdown-cv-mdcv-pdf-1   |          
markdown-cv-mdcv-pdf-1   | l.27 \defaultfontfeatures
markdown-cv-mdcv-pdf-1   | 
markdown-cv-mdcv-pdf-1 exited with code 43