* Move all existing *.tex into de/
* Prepare en (English) directory
* Select ngerman for German cheatsheets as default
* First translated Python cheatsheet for English: python-cheatsheet.tex
* Adapt sty files to English language
  * Move *.sty files into sty directory
  * Require package iflang
  * Use \IfLanguageName to test for "ngerman"; use specific typographic
    quotes for German, otherwise use English quotes for \iqq
  * Move \gquote, depend definition on \iqq
  * Move babel's \addto{\captionsgerman} to \IfLanguageName block
* Ignore file which end in ~ (.gitignore)
* Adapt .gitlab-ci.yml to build en
* Prepare build.sh script for English
  Allow to set PDF_LANGUAGES. Contains a list of language
  folders, separated by space. For example, the following
  line builds English cheatsheets only:

  $ PDF_LANGUAGES="en" ./build.sh
* Update README