Report detexed word count in CI and generate badge

Report detexed word count in CI and generate badge that may be added to the README.
May be done roughly as follows with the texlive image:

```bash
    - apt-get update && apt-get install -y python3-pip
    - pip install anybadge
    - words=$(detex main.tex | wc -w)
    - echo "Word count is $words"
    - anybadge --label "Word count" --value $words -f wordCount.svg -c lightslategray
```