Update to Dart 3.5 and web 1.1 (#3915)

Author: parlough

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 8.3.1-wip
+
+* Require Dart 3.5 or later.
+
 ## 8.3.0
 
 * The URL for library pages has moved "<em>library-name</em>-library.html" to

dartdoc_options.yaml

@@ -1,4 +1,4 @@
 dartdoc:
   linkToSource:
     root: '.'
-    uriTemplate: 'https://github.com/dart-lang/dartdoc/blob/v8.3.0/%f%#L%l%'
+    uriTemplate: 'https://github.com/dart-lang/dartdoc/blob/v8.3.1-wip/%f%#L%l%'