Move into wp-content path

Signed-off-by: Adrian Nöthlich <git@promasu.tech>

wp-content/plugins/github-updater/vendor/afragen/singleton/README.md

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+# singleton
+
+This is a singleton static proxy generator that I use in several projects instead of creating true Singletons. It was inspired by [Alain Schlesser’s post on Singletons](https://www.alainschlesser.com/singletons-shared-instances/).
+
+I’ve moved this library into it’s own repository so that I will be better able to include it via composer.
+
+I have written it to work with PSR-4.
+
+`composer require afragen/singleton:dev-master`
+
+When using this Singleton class in your project you will create an array of class instances.
+
+## Usage
+
+```php
+@param string               $class_name
+@param object               $caller     Originating object.
+@param null|array|\stdClass $options
+
+Singleton::get_instance( $class_name, $calling_class, $options );
+```
+
+This will usually be called as follows.
+
+`Singleton::get_instance( 'MyClass', $this );`
+
+The class object created will also pass the calling object as `$instance[$class_name]->caller`.
+
+I do my best to automatically determine the namespace of the class. If the class is in a subfolder of `src` it will need to be designated in the call as follows.
+
+If PSR-4 is set for the `src` directory and the class lives in `src/MySubDir/MyClass` the corresponding call would be as follows.
+
+`Singleton::get_instance( 'MySubDir\MyClass', $this );`
+
+I’m still learning how to properly set up using composer so this may be updated along the way.