Update readme

Author: adamjosefus

Diff for: README.md

@@ -1 +1,41 @@
-# deno-caching
+# Caching
+
+## `Cache`
+
+```ts
+const cache = new Cache<string>();
+
+const cacheKey = 'abc123';
+
+/**
+ * Load from cache.
+ * If not found, value will be generated and stored in cache.
+ */
+cache.load(cacheKey, () => {
+    const result = 'Lorem ipsum';
+
+    // Some expensive operation
+    // ...
+
+    return result
+}); // -> string
+
+
+/**
+ * Load from cache.
+ */
+cache.load(cacheKey); // -> string | undefined
+
+
+/**
+ * Save to cache.
+ */
+cache.save(cacheKey, 'Lorem ipsum');
+
+
+/**
+ * Check if cache exists.
+ */
+cache.has(cacheKey); // -> boolean
+
+```