Remove is-plain-object dependency

Co-authored-by: Mark Wubben <[email protected]>

Author: Conaclos

index.js

@@ -2,10 +2,13 @@
 const path = require('path');
 
 const escapeStringRegexp = require('escape-string-regexp');
-const isPlainObject = require('is-plain-object');
 
 const pkg = require('./package.json');
 
+function isPlainObject(x) {
+	return x !== null && typeof x === 'object' && Reflect.getPrototypeOf(x) === Object.prototype;
+}
+
 function isValidExtensions(extensions) {
 	return Array.isArray(extensions) &&
 		extensions.length > 0 &&

package.json

@@ -19,8 +19,7 @@
     "test": "xo && nyc ava"
   },
   "dependencies": {
-    "escape-string-regexp": "^2.0.0",
-    "is-plain-object": "^3.0.0"
+    "escape-string-regexp": "^2.0.0"
   },
   "devDependencies": {
     "ava": "^3.0.0",