fix docs

External links render as code, for example: https://www.dartdocs.org/documentation/collection/1.9.0/collection/compareNatural.html
diff --git a/lib/src/comparators.dart b/lib/src/comparators.dart
index 4995100..ca2b3c7 100644
--- a/lib/src/comparators.dart
+++ b/lib/src/comparators.dart
@@ -145,7 +145,7 @@
   return defaultResult.sign;

 }

 

-/// Compares strings [a] and [b] according to [natural sort ordering].

+/// Compares strings [a] and [b] according to [natural sort ordering][].

 ///

 /// A natural sort ordering is a lexical ordering where embedded

 /// numerals (digit sequences) are treated as a single unit and ordered by

@@ -175,7 +175,7 @@
 }

 

 /// Compares strings [a] and [b] according to lower-case

-/// [natural sort ordering].

+/// [natural sort ordering][].

 ///

 /// ASCII letters are converted to lower case before being compared, like

 /// for [compareAsciiLowerCase], then the result is compared like for

@@ -212,7 +212,7 @@
 }

 

 /// Compares strings [a] and [b] according to upper-case

-/// [natural sort ordering].

+/// [natural sort ordering][].

 ///

 /// ASCII letters are converted to upper case before being compared, like

 /// for [compareAsciiUpperCase], then the result is compared like for