Upkeep spring 2025

[teunbrand]

This PR aims to fix #6439.

Few notes:

• Didn't commit to using air yet, as discussed
• \(x) syntax only when functions fit in one line in examples, not internal code
• Chunk headers were already in yaml style
• Already using expect_snapshot(error = TRUE)
• Only bumped MIT licence year, as we want to retain the 'core developers' as authors
• I assumed some GHA rules are custom, so I just bumped versions
• Already using alt text
• Not sure wether the Re-publish released site applies here