Parse links in wiki syntax [[term]]

This way we can use this faster syntax which is also supported by
Obsidian.

lib/core/link.dart

@@ -51,6 +51,14 @@ class LinkExtractor implements md.NodeVisitor {
       var url = el.attributes['href'];
       var link = Link(term: title, filePath: url);
       links.add(link);
+      return;
+    }
+
+    if (tag == 'wikiLink') {
+      var value = el.attributes['value'];
+      var link = Link(term: value, filePath: null);
+      links.add(link);
+      return;
     }
   }
 
@@ -61,3 +69,17 @@ class LinkExtractor implements md.NodeVisitor {
     return links;
   }
 }
+
+class MetaLinkSyntax extends md.InlineSyntax {
+  static final String _pattern = '\\[\\[([^\\[\\]]+)\\]\\]';
+
+  MetaLinkSyntax() : super(_pattern);
+
+  @override
+  bool onMatch(md.InlineParser parser, Match match) {
+    md.Element el = md.Element.withTag('wikiLink');
+    el.attributes['value'] = '${match[1].trim()}';
+    parser.addNode(el);
+    return true;
+  }
+}

lib/core/note.dart

@@ -450,6 +450,7 @@ class Note with NotesNotifier {
     final doc = md.Document(
       encodeHtml: false,
       extensionSet: md.ExtensionSet.gitHubFlavored,
+      inlineSyntaxes: [MetaLinkSyntax()],
     );
 
     var lines = body.replaceAll('\r\n', '\n').split('\n');
@@ -459,6 +460,11 @@ class Note with NotesNotifier {
     var links = <Link>[];
     for (var l in possibleLinks) {
       var path = l.filePath;
+      if (path == null) {
+        links.add(l);
+        continue;
+      }
+
       var isLocal = (path.startsWith('/') || path.startsWith('.')) &&
           !path.contains('://');
       if (isLocal) {

test/note_test.dart

@@ -140,6 +140,26 @@ title: Foo
       expect(links.length, 2);
     });
 
+    test('Should parse wiki style links', () async {
+      var content = "[[GitJournal]] needs some [[Wild Fire]]";
+
+      var notePath = p.join(tempDir.path, "note63.md");
+      await File(notePath).writeAsString(content);
+
+      var parentFolder = NotesFolderFS(null, tempDir.path);
+      var note = Note(parentFolder, notePath);
+      await note.load();
+
+      var links = await note.fetchLinks();
+      expect(links[0].filePath, null);
+      expect(links[0].term, "GitJournal");
+
+      expect(links[1].filePath, null);
+      expect(links[1].term, "Wild Fire");
+
+      expect(links.length, 2);
+    });
+
     test('Should detect file format', () async {
       var content = """---
 title: Foo