Move all Kind constants to its own package

See #11256

resources/page/page_kinds.go

@@ -12,36 +12,3 @@
 // limitations under the License.
 
 package page
-
-import "strings"
-
-const (
-	KindPage = "page"
-
-	// The rest are node types; home page, sections etc.
-
-	KindHome    = "home"
-	KindSection = "section"
-
-	// Note that before Hugo 0.73 these were confusingly named
-	// taxonomy (now: term)
-	// taxonomyTerm (now: taxonomy)
-	KindTaxonomy = "taxonomy"
-	KindTerm     = "term"
-)
-
-var kindMap = map[string]string{
-	strings.ToLower(KindPage):     KindPage,
-	strings.ToLower(KindHome):     KindHome,
-	strings.ToLower(KindSection):  KindSection,
-	strings.ToLower(KindTaxonomy): KindTaxonomy,
-	strings.ToLower(KindTerm):     KindTerm,
-
-	// Legacy, pre v0.53.0.
-	"taxonomyterm": KindTaxonomy,
-}
-
-// GetKind gets the page kind given a string, empty if not found.
-func GetKind(s string) string {
-	return kindMap[strings.ToLower(s)]
-}