Better scaling of images in HTML output
Turn on the previously disabled automatic scaling of images in HTML
output. To avoid images looking too large on nowadays-normal screens,
restrict the width to 75% on such screens.
Some work is still necessary because SVG images without a viewBox
still won't scale, but that will a separate patch.
Discussion: https://www.postgresql.org/message-id/flat/
6d2442d1-84a2-36ef-e014-
b6d1ece8a139%40postgresql.org