Add the scaffolding for automatically adding Wiki Links

The idea is that on save a Note, terms which have already been used
before as Wiki Links should automatically be converted into Wiki Links.

lib/core/processors/wiki_links_auto_add.dart

@@ -0,0 +1,31 @@
+import 'package:gitjournal/core/note.dart';
+import 'package:gitjournal/core/notes_folder.dart';
+
+class WikiLinksAutoAddProcessor {
+  final NotesFolder rootFolder;
+
+  WikiLinksAutoAddProcessor(this.rootFolder);
+
+  void process(Note note) {}
+
+  String processBody(String body, List<String> tags) {
+    for (var tag in tags) {
+      var regexp = RegExp('\\b$tag\\b');
+      int start = 0;
+      while (true) {
+        var i = body.indexOf(regexp, start);
+        if (i == -1) {
+          break;
+        }
+
+        body = _replace(body, i, i + tag.length, '[[$tag]]');
+        start = i + tag.length + 4;
+      }
+    }
+    return body;
+  }
+}
+
+String _replace(String body, int startPos, int endPos, String replacement) {
+  return '${body.substring(0, startPos)}$replacement${body.substring(endPos)}';
+}

test/processors/wiki_links_auto_add_test.dart

@@ -0,0 +1,21 @@
+import 'package:test/test.dart';
+
+import 'package:gitjournal/core/processors/wiki_links_auto_add.dart';
+
+void main() {
+  test('Should process body', () {
+    var body =
+        "GitJournal is the best? And it works quite well with Foam, Foam and Obsidian.";
+
+    var p = WikiLinksAutoAddProcessor(null);
+    var newBody = p.processBody(body, ['GitJournal', 'Foam', 'Obsidian']);
+    var expectedBody =
+        "[[GitJournal]] is the best? And it works quite well with [[Foam]], [[Foam]] and [[Obsidian]].";
+
+    expect(newBody, expectedBody);
+  });
+
+  // Add a test to see if processing a Note works
+  // FIXME: Make sure the wiki link terms do not have special characters
+  // FIXME: WHat about piped links?
+}