Add `docsUrl` method to the `Screen` class and add docs for Deep links screen (#7167)

* Add `docsUrl` method to the `Screen` class

* typo

* formatting

packages/devtools_app/lib/src/framework/status_line.dart

diff --git a/packages/devtools_app/lib/src/framework/status_line.dart b/packages/devtools_app/lib/src/framework/status_line.dart
index 5e31f37..e0330c1 100644
--- a/packages/devtools_app/lib/src/framework/status_line.dart
+++ b/packages/devtools_app/lib/src/framework/status_line.dart
@@ -216,7 +216,8 @@
       icon: Icons.library_books_outlined,
       link: Link(
         display: screenWidth <= MediaSize.xs ? 'Docs' : 'Read docs',
-        url: 'https://docs.flutter.dev/tools/devtools/$docPageId',
+        url: screen.docsUrl ??
+            'https://docs.flutter.dev/tools/devtools/$docPageId',
         gaScreenName: screen.screenId,
         gaSelectedItemDescription: gac.documentationLink,
       ),

packages/devtools_app/lib/src/screens/deep_link_validation/deep_links_screen.dart

diff --git a/packages/devtools_app/lib/src/screens/deep_link_validation/deep_links_screen.dart b/packages/devtools_app/lib/src/screens/deep_link_validation/deep_links_screen.dart
index 4e8fb23..3a6dff1 100644
--- a/packages/devtools_app/lib/src/screens/deep_link_validation/deep_links_screen.dart
+++ b/packages/devtools_app/lib/src/screens/deep_link_validation/deep_links_screen.dart
@@ -22,6 +22,12 @@
   // @override
   // String get docPageId => id;
 
+  // TODO(https://github.com/flutter/devtools/issues/6013): consider removing
+  // this docs url override when documentation is written specifically for the
+  // deep links tool.
+  @override
+  String get docsUrl => 'https://docs.flutter.dev/ui/navigation/deep-linking';
+
   @override
   Widget build(BuildContext context) {
     return const DeepLinkPage();

packages/devtools_app/lib/src/shared/screen.dart

diff --git a/packages/devtools_app/lib/src/shared/screen.dart b/packages/devtools_app/lib/src/shared/screen.dart
index 08abcba..ee2f64b 100644
--- a/packages/devtools_app/lib/src/shared/screen.dart
+++ b/packages/devtools_app/lib/src/shared/screen.dart
@@ -293,10 +293,19 @@
   ValueListenable<bool> get showIsolateSelector =>
       const FixedValueListenable<bool>(false);
 
-  /// The id to use to synthesize a help URL.
+  /// The documentation URL to use for this screen.
+  ///
+  /// If this returns a null value, [docPageId] will be used to create a
+  /// documentation URL.
+  String? get docsUrl => null;
+
+  /// The id to use to create a documentation URL for this screen.
   ///
   /// If the screen does not have a custom documentation page, this property
   /// should return `null`.
+  ///
+  /// If [docsUrl] returns a non-null value, [docsUrl] will be used instead of
+  /// creating a documentation url using [docPageId].
   String? get docPageId => null;
 
   double approximateTabWidth(