Update README.md

README.md

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-# service-container
 Lightweight yet powerful implementation of dependancy injection container with autowiring.
+
+## Installation
+Use [Composer] to install the package:
+```
+composer require intraworlds/service-container
+```
+
+## Usage
+The container is implementing standard PSR-11 interface. You can use it with autowiring out-of-the-box.
+
+Let's say that we're building a cache client. This client will not implement a cache directly but only provides common API - it will depend on given adapter.
+
+We'll start will start with defining memory adapter
+```php
+namespace Acme\Cache;
+
+class MemoryAdapter {
+  function get(string $key): string {}
+  function set(string $key, string $string): void {}
+}
+```
+Cache client
+```php
+namespace Acme\Cache;
+
+class Client {
+  private $adapter;
+
+  function __construct(MemoryAdapter $adapter) {
+    $this->adapter = $adapter;
+  }
+
+  function get(string $key) {
+    $string = $this->adapter->get($key);
+    return unserialize($string);
+  }
+
+  function set(string $key, $value): void {
+    $string = serialize($value);
+    $this->adapter->set($key, $string);
+  }
+}
+```
+Now in the main program we can instantiate cache client with ease - dependancy of the client will be resolved automatically.
+```php
+namespace Acme;
+
+use IW\ServiceContainer;
+
+$container = new ServiceContainer;
+$client = $container->get(Cache\Client::class);
+```
+Our still implementing serialization by itself. Let's move it into dependancy.
+```php
+namespace Acme\Cache;
+
+class PhpSerializer {
+  function serialize($value): string {}
+  function unserialize(string $string) {}
+}
+```
+And little change in the client.
+```php
+namespace Acme\Cache;
+
+class Client {
+  private $adapter;
+
+  function __construct(MemoryAdapter $adapter, PhpSerializer $serializer) {
+    $this->adapter = $adapter;
+    $this->serializer = $serializer;
+  }
+
+  function get(string $key) {
+    $string = $this->adapter->get($key);
+    return $this->serializer->unserialize($string);
+  }
+
+  function set(string $key, $value): void {
+    $string = $this->serializer->serialize($value);
+    $this->adapter->set($key, $string);
+  }
+}
+```
+Our main code will stay the same.
+```php
+$client = $container->get(Cache\Client::class);
+```
+
+
+## License
+All contents of this package are licensed under the [MIT license].
+
+[Composer]: https://getcomposer.org
+[MIT license]: LICENSE