Update MD051/link-fragments to allow HTML's implicit "#top" fragment (fixes #1488).

test/snapshots/markdownlint-test-scenarios.mjs.md

@@ -25749,6 +25749,26 @@ Generated by [AVA](https://avajs.dev).
             'link-fragments',
           ],
         },
+        {
+          errorContext: '[Invalid](#ToP)',
+          errorDetail: 'Expected: #top; Actual: #ToP',
+          errorRange: [
+            1,
+            15,
+          ],
+          fixInfo: {
+            deleteCount: 4,
+            editColumn: 11,
+            insertText: '#top',
+          },
+          lineNumber: 339,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
       ],
       fixed: `# Valid/Invalid Link Fragments␊
       ␊
@@ -26084,6 +26104,12 @@ Generated by [AVA](https://avajs.dev).
       ␊
       [Invalid](#C11-L4C31) {MD051}␊
       ␊
+      ## Implicit Fragments␊
+      ␊
+      [Valid](#top)␊
+      ␊
+      [Invalid](#top) {MD051}␊
+      ␊
       <!-- markdownlint-configure-file {␊
         "emphasis-style": false,␊
         "heading-style": false,␊