Add "static analysis" Composer keyword (#2)

As per https://getcomposer.org/doc/04-schema.md#keywords by including "static analysis" as a keyword in the `composer.json` file, Composer 2.4.0-RC1 and later will prompt users if the package is installed with `composer require` instead of `composer require --dev`. See composer/composer#10960 for more info.

The "phpcs" keyword is to match other coding-standards packages.

Author: GaryJones

composer.json

@@ -1,6 +1,7 @@
 {
     "name": "codeigniter/coding-standard",
     "type": "library",
+    "keywords": [ "phpcs", "static analysis" ],
     "description": "Official Coding Standards for CodeIgniter based on PHP CS Fixer",
     "license": "MIT",
     "authors": [