Guidelines authors

[astamm]

I updated the authors guidelines to address most items referenced in computorg#14.

Things left to do:

• Add guidelines for handling dependencies in Julia
• A pass at example template contents for accuracy and to avoid saying things already said in guidelines? Maybe looking at shortcodes in quarto.
• Remove “How to automatically publish the HTML of my contribution to a website?” From the FAQ ?
• Explain that it is possible to use multiple languages provided that we use the knitr engine.