[Request] Ability to use operator within script

Just wanted to quickly say that this is a great addon and very easy to use! I haven't had any issues with it.

However, I would like the ability to use the operator/addon within a custom script, as it helps me to apply modifiers and join meshes together to get it ready for export.

Unfortunately, the operator does not work when I pass in a list of dictionaries via `bpy.ops.object.apply_modifiers_with_shape_keys(collection_property = my_list)` with my object selected, as I get an error that it can't find the `key_block` attribute.

I am sure it is low on your priority, but some way to import the class or function to apply modifiers for shape keys in a script would be amazing!

Start at the bpy.ops.object.apply_modifiers_with_shape_keys entry point and reproduce the key_block error using a list of dictionaries passed as collection_property. Trace how the operator handles the selected object and determine what script-facing import or callable is needed; done means the modifier-and-shape-key operation can be invoked from a custom script without that error.

Written by the indexing model from the issue text.