Hash CSS assets to break caching when they change

[Minoru]

I cache CSS for a week, so any changes to it tend to break the site because old CSS is used with new markup. The solution to this is "asset hashing". Some pointers:

• https://groups.google.com/g/hakyll/c/zdkQlDsj9lQ
• https://mikey.bike/j/2021/10/asset-hashing.html
• https://jezenthomas.com/2022/08/static-asset-hashing-in-hakyll/