Improve formatting of spotify blog post

[ludekcizinsky]

• Make sure we use heading level 3 for the titles
• Make sure all images have good resolution, the architecture pic looks bit shit :/
• Add missing image

[mikasenghaas]

Whoops, my bad. I was batch-downscaling all images via CLI and it seemed seemed fine on all the images I looked at in terms of resolution, while giving significantly smaller file sizes. Chris might have already done some downscaling before tho, so my additional downscaling was too much. Will fix tomorrow if you don’t do it

[mikasenghaas]

Why H3? Doesn’t H2 seem more natural? If we have a large H2 section we have the option of using H3s to divide it. Can’t really do that if the whole section is H3 in the first place, because H4s look shit