Add "static analysis" Composer keyword

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.

composer.json

@@ -2,7 +2,7 @@
   "name" : "phpcompatibility/php-compatibility",
   "description" : "A set of sniffs for PHP_CodeSniffer that checks for PHP cross-version compatibility.",
   "type" : "phpcodesniffer-standard",
-  "keywords" : [ "compatibility", "phpcs", "standards" ],
+  "keywords" : [ "compatibility", "phpcs", "standards", "static analysis" ],
   "homepage" : "http://techblog.wimgodden.be/tag/codesniffer/",
   "license" : "LGPL-3.0-or-later",
   "authors" : [ {