During migration, while we launch Redocly with -d content, the static
files need to be in content. Eventually, when we stop using -d, we need
to move the files again.
Previously:
/assets : static assets used by templates
/img : images used in documentation (mostly)
Now:
/content/static : static assets used by templates
/img : images used in documentation (mostly)
Eventually:
/static : static assets used by templates
/docs/img : images used in documentation
