Add support (autocompletion) for TranslatableMessage class

[Tomsgu]

Hey there,

From symfony 5.2 there is a TranslatableMessage class. Very useful when using in forms, because symfony can extract those translation elements by e.g. bin/console translation:extract command. It would be sweet to have autocompletion here.

Also I wanted to help the plugin by adding a record to Method references, but it seems not working. My guess is that it can't spot __construct() method when using new keyword? Or am I missing something?