add composer.json

used https://github.com/jbrinley/wp-git-deploy/blob/master/composer.json as a starting point

composer.json

@@ -0,0 +1,15 @@
+{
+	"name": "jbrinley/wp-router",
+	"description": "Provides a simple API for mapping requests to callback functions.",
+	"type": "wordpress-plugin",
+	"authors": [
+		{
+			"name": "Jonathan Brinley",
+			"email": "[email protected]"
+		}
+	],
+	"require": {
+		"php": ">=5.2.0"
+	},
+	"minimum-stability": "dev"
+}

readme.txt

@@ -145,6 +145,7 @@ Creating or changing routes should always occur in the context of the `wp_router
 = 0.6 =
 
 * Make magic methods public to avoid fatal with PHP 7.3
+* Add `composer.json` to ease others' including
 
 = 0.5 =