Spelling: Oxford spelling

See: https://en.wikipedia.org/wiki/Oxford_spelling

As far as I could see we mostly use the -ise variant, but this is not consistent

Search the repository's Markdown documentation for inconsistent -ise and -ize spellings, starting with a repository-wide text search. Confirm the project's preferred Oxford spelling and identify every affected passage. Done means the relevant documentation consistently follows the chosen spelling.

Written by the indexing model from the issue text.