markup/goldmark: Change link and image render hook enablement to enums

Closes #13535

helpers/general.go

@@ -255,6 +255,27 @@ func SliceToLower(s []string) []string {
 	return l
 }
 
+// StringSliceToList formats a string slice into a human-readable list.
+// It joins the elements of the slice s with commas, using an Oxford comma,
+// and precedes the final element with the conjunction c.
+func StringSliceToList(s []string, c string) string {
+	const defaultConjunction = "and"
+
+	if c == "" {
+		c = defaultConjunction
+	}
+	if len(s) == 0 {
+		return ""
+	}
+	if len(s) == 1 {
+		return s[0]
+	}
+	if len(s) == 2 {
+		return fmt.Sprintf("%s %s %s", s[0], c, s[1])
+	}
+	return fmt.Sprintf("%s, %s %s", strings.Join(s[:len(s)-1], ", "), c, s[len(s)-1])
+}
+
 // IsWhitespace determines if the given rune is whitespace.
 func IsWhitespace(r rune) bool {
 	return r == ' ' || r == '\t' || r == '\n' || r == '\r'