add 3 caching implementations for various use cases

readme.md

@@ -2,3 +2,67 @@
 In-memory caching/memoization utilities
 
 ---
+
+## Install
+
+```bash
+npm install --save @js/memo
+```
+
+## Usage
+
+```ts
+import { memo } from '@js/memo';
+
+function get_data_from_slow_source(name: string) : string {
+	// ....
+}
+
+const get_data_cached = memo({
+	func: get_data_from_slow_source,
+	ttl: 30_000,
+});
+```
+
+### Custom cache key generation
+
+```ts
+import { memo } from '@js/memo';
+
+interface SomeObject {
+	id: string;
+	foo: string;
+	bar: number;
+	baz: {
+		qux: string;
+	};
+}
+
+function get_data_from_slow_source(obj: SomeObject) : string {
+	// ....
+}
+
+const get_data_cached = memo({
+	func: get_data_from_slow_source,
+	ttl: 30_000,
+
+	// Pull just the `id` field from the first parameter to use
+	// as the cache key
+	key([ obj ]) {
+		return obj.id;
+	},
+});
+```
+
+### Simple functions with no params
+
+```ts
+
+import { memo_simple } from '@js/memo';
+
+function get_data_from_slow_source() : string {
+	// ....
+}
+
+const get_data_cached = memo_simple(30_000, get_data_from_slow_source);
+```