docs: add all-contributors as a contributor for doc #10

Add @all-contributors as a contributor for doc.

This was requested by seanpm2001 [in this comment](https://github.com/seanpm2001/Its-time-to-cut-WideVine-DRM/issues/7#issuecomment-1002301516)

https://github.com/seanpm2001/Its-time-to-cut-WideVine-DRM/pull/10
