Update rules for Web IDE and Content Editor packages

It updates the following dependency rules:

• It always assigns as initial reviewers @ealcantara and @pslaughter for @gitlab/web-ide package updates.
• It tracks remark, rehype, and unist package updates used by the GFM frontend parser, which in turn, is used by the Content Editor: https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/lib/gfm/index.js#L4