Update phpunit to version 9.

As we dictate library supports 7.3 and above it makes sense to bump the
phpunit to version 9 (also 7.3 and above).

Further to this, I've updated mockery, tidied up some formatting and
introduced an .editorconfig file as well as dependabot.

.editorconfig

@@ -0,0 +1,11 @@
+root = true
+
+[*]
+indent_size = 4
+indent_style = space
+trim_trailing_whitespace = true
+
+[*.{php,js,ts,css,scss,pot,po}]
+end_of_line = lf
+indent_style = tab
+insert_final_newline = true

.github/dependabot.yml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+    -   package-ecosystem: composer
+        directory: "/"
+        registries: "*"
+        schedule:
+            interval: daily
+        open-pull-requests-limit: 10
+        commit-message:
+            prefix: "[DEPS]"
+        ignore:
+            # Ignore PHPUnit major updates
+            -   dependency-name: "phpunit/phpunit"
+                update-types: [ "version-update:semver-major" ]

composer.json

@@ -1,41 +1,49 @@
 {
-	"name" : "boxuk/wp-muplugin-loader",
-	"description" : "A drop-in MU Plugin loader for WordPress",
-	"keywords" : ["wordpress", "muplugin", "loader"],
-	"type" : "composer-plugin",
-	"license" : "MIT",
-	"minimum-stability": "stable",
-	"prefer-stable": true,
-	"authors" : [
-		{
-			"name" : "Box UK",
-			"email": "developers@boxuk.com"
-		},
-		{
-			"name" : "Luke Woodward",
-			"email": "woodward.lucas@gmail.com"
-		}
-	],
-	"autoload": {
-		"psr-4": { "LkWdwrd\\Composer\\": "src/lkwdwrd/Composer" }
-	},
-	"autoload-dev": {
-		"psr-4": { "LkWdwrd\\Composer\\Tests\\":  "tests/phpunit/Composer" }
-	},
-	"extra": {
-		"class": "LkWdwrd\\Composer\\MULoaderPlugin"
-	},
-	"require": {
-		"php": "^7.3 || ^8.0",
-		"composer-plugin-api": "^1.0 || ^2.0"
-	},
-	"require-dev" : {
-		"10up/wp_mock": "^0.4",
-		"composer/composer": "^1.10 || ^2.0",
-		"phpunit/phpunit": "^8.5",
-		"mockery/mockery": "~1.3.3"
-	},
-	"scripts" : {
-		"test" : "vendor/bin/phpunit --colors"
-	}
+    "name": "boxuk/wp-muplugin-loader",
+    "description": "A drop-in MU Plugin loader for WordPress",
+    "keywords": [
+        "wordpress",
+        "muplugin",
+        "loader"
+    ],
+    "type": "composer-plugin",
+    "license": "MIT",
+    "minimum-stability": "stable",
+    "prefer-stable": true,
+    "authors": [
+        {
+            "name": "Box UK",
+            "email": "developers@boxuk.com"
+        },
+        {
+            "name": "Luke Woodward",
+            "email": "woodward.lucas@gmail.com"
+        }
+    ],
+    "autoload": {
+        "psr-4": {
+            "LkWdwrd\\Composer\\": "src/lkwdwrd/Composer"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "LkWdwrd\\Composer\\Tests\\": "tests/phpunit/Composer"
+        }
+    },
+    "extra": {
+        "class": "LkWdwrd\\Composer\\MULoaderPlugin"
+    },
+    "require": {
+        "php": "^7.3 || ^8.0",
+        "composer-plugin-api": "^1.0 || ^2.0"
+    },
+    "require-dev": {
+        "10up/wp_mock": "^0.4",
+        "composer/composer": "^1.10 || ^2.0",
+        "phpunit/phpunit": "^9",
+        "mockery/mockery": "~1.3"
+    },
+    "scripts": {
+        "test": "vendor/bin/phpunit --colors"
+    }
 }