Add readme

Author: sidvishnoi

README.md

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+# Compact Prefix Tree
+
+A serializable compact prefix tree (also known as Radix tree or Patricia tree or space-optimized trie) implementation in JavaScript.
+
+## Usage
+
+### Installation
+
+``` bash
+npm install compact-prefix-tree
+```
+
+### General Usage
+
+``` js
+const { CompactPrefixTree } = require("compact-prefix-tree");
+
+const items = [
+  "http://www.example.com/foo/",
+  "http://www.example.com/baz/",
+];
+
+// create a trie from array of strings
+const trie = new CompactPrefixTree(items);
+// can add items later
+trie.add("http://www.example.com/john/");
+
+// look for a prefix of a word
+const p1 = trie.prefix("http://www.example.com/john/doe");
+// p1: { prefix: "http://www.example.com/john/", isProper: true }
+const p2 = trie.prefix("http://www.example.com/bazinga");
+// p2: { prefix: "http://www.example.com/", isProper: false }
+// above is not proper as it doesn't exist in list of items provided
+```
+
+### Serialization
+
+``` js
+const { CompactPrefixTree, getWordsFromTrie } = require("compact-prefix-tree");
+const items = [
+  "http://www.example.com/foo/",
+  "https://www.example.com/baz/",
+];
+const trie = new CompactPrefixTree(items);
+const serialized = JSON.stringify(trie.T);
+// {
+//   "http": {
+//     "://www.example.com/foo/": null,
+//     "s://www.example.com/baz/": null
+//   }
+// }
+
+const words = getWordsFromTrie(JSON.parse(serialized));
+// Set(2) {"http://www.example.com/foo/" "https://www.example.com/baz/"}
+
+const trie2 = new CompactPrefixTree(Array.from(words));
+// assert(isEqual(trie.items, trie2.items));
+```
+
+## License
+
+[MIT License] Copyright 2018 Sid Vishnoi (https://sidvishnoi.github.io)