Improve docs and add composer package keywords

Author: e1himself

README.md

@@ -2,7 +2,9 @@
 
 # NullContainer
 
-`NullContainer` is a [PSR-11](https://www.php-fig.org/psr/psr-11/) container implementation that is always empty. 
+`NullContainer` is a [PSR-11](https://www.php-fig.org/psr/psr-11/) container implementation that is always empty.
+
+This is a [NullObject](https://en.wikipedia.org/wiki/Null_object_pattern) pattern implementation for PSR-11.
 
 This is useful when you want to provide an optional `ContainerInterface` dependency, 
 but don't want to deal with nullable values.

composer.json

@@ -2,6 +2,14 @@
     "name": "technically/null-container",
     "description": "Null (always empty) PSR-11 container implementation",
     "type": "library",
+    "keywords": [
+        "php",
+        "psr-11",
+        "psr-container",
+        "container",
+        "null",
+        "null-object"
+    ],
     "require": {
         "php": ">=7.1",
         "psr/container": "^1.0"