Document best practices when adding images to documentation

[tjanez]

Some obvious steps would be:

1. Document how to choose an appropriate image format (JPG, PNG).
2. Add CLI command that automatically reduces size of images.
3. Document how to apply it before adding images to git history.
4. Document how to sensibly name images.

[lukaw3d]

For 1. and 2.:

• 01a93e1

shopt -s globstar
for i in docs/**/*.png; do
  # imagemagick to convert to sRGB color profile
  convert "$i" -profile /usr/share/color/icc/colord/sRGB.icc -strip "$i"
  # @squoosh/cli to reduce file size
  npx squoosh-cli \
    --quant '{"enabled": true, "zx": 0, "maxNumColors": 256, "dither": 1}' \
    --oxipng '{"level":2,"interlace":false}' --output-dir "`dirname $i`" "$i"
done

• 4d7a3fb

shopt -s globstar
for i in docs/**/*.jpg; do
  # imagemagick to convert to sRGB color profile
  convert "$i" -profile /usr/share/color/icc/colord/sRGB.icc -strip "$i"
  # @squoosh/cli to reduce file size
  npx squoosh-cli --mozjpeg '{"quality":75}' --output-dir "`dirname $i`" "$i"
done