feature: remove files with the draft extension prefix

[webketje]

The aim of this feature is to allow both a draft version and a "published" version to co-exist, a common use case in existing websites.
A file my-post.md could then co-exist with my-post.draft.md. The file is always removed, but when drafts are enabled the pointer to my-post.md is replaced with the file at my-post.draft.md