Userland: Add new app called Assistant

'Assistant' is similar to macOS spotlight where you can quickly open a
text input, start typing, and hit 'enter' to launch apps or open
directories.

Userland/Applications/Assistant/FuzzyMatch.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2021, Spencer Dixon <spencercdixon@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <AK/Tuple.h>
+
+namespace Assistant {
+
+struct FuzzyMatchResult {
+    bool matched { false };
+    int score { 0 };
+};
+
+// This fuzzy_match algorithm is based off a similar algorithm used by Sublime Text. The key insight is that instead
+// of doing a total in the distance between characters (I.E. Levenshtein Distance), we apply some meaningful heuristics
+// related to our dataset that we're trying to match to build up a score. Scores can then be sorted and displayed
+// with the highest at the top.
+//
+// Scores are not normalized between any values and have no particular meaning. The starting value is 100 and when we
+// detect good indicators of a match we add to the score. When we detect bad indicators, we penalize the match and subtract
+// from its score. Therefore, the longer the needle/haystack the greater the range of scores could be.
+FuzzyMatchResult fuzzy_match(String needle, String haystack);
+
+}