docs: Clarify usage of archetypes provided by themes
docs: Clarify usage of archetypes provided by themes

tubo028/hugo,jygastaud/hugo,fedelibre/hugo,mayah/hugo,mitchchn/hugo,anthonyfok/hugo,mdhender/hugo,jygastaud/hugo,fedelibre/hugo,anthonyfok/hugo,fedelibre/hugo,mitchchn/hugo,fedelibre/hugo,tubo028/hugo,anthonyfok/hugo,gohugoio/hugo,mdhender/hugo,MarkDBlackwell/hugo,digitalcraftsman/hugo,digitalcraftsman/hugo,mdhender/hugo,mayah/hugo,mdhender/hugo,MarkDBlackwell/hugo,gohugoio/hugo,gohugoio/hugo