better contrast for blog post headings

[yochannah]

currently blog posts has a nice blurry text-shadow - but this doesn't always provide enough contrast on the image in the blog header. Example: https://we-are-ols.org/posts/2026/06/01/rfp-for-open-science-coalition/

screenshot - the authors names are invisible!

a 1px distance low-blue white shadow, or even two, might help? it should work with many kinds of background.