Better support for serialized/nested inputs

Hi, I noticed that your plugin handles nested inputs (ie: <input name="some_input[99]" value="2" /> as strings when posting data. This is different from how a lot of plugins expect to receive the data.. ie: in an array)

I propose some tweaks to better handle this type of inputs… I tested this with variable products, Product Addons, and two of my plugins: Name Your Price, and Mix and Match Products… so far seems to work.

https://gist.github.com/helgatheviking/56a53a80ba7a0c58b659700f2bc40124

You’ll also note the addition of qlwcajax_product_supported_types in the class-plugins.php to allow for the display on additional product types like so:

add_filter( 'qlwcajax_product_supported_types', function( $types ) {
        $types[] = 'mix-and-match';
	return $types;
} );