Allow to filter assemblies by type

Is your feature request related to a problem? Please describe.

Currently there only a simple filter in assemblies admin. We need to add filter by "Assembly type", taking into account values in the AssembliesTypes model.

Describe the solution you'd like

Create a filter in the admin that allows to filter by Assembly type

Describe alternatives you've considered

No alternatives considered

Additional context

Pull request: https://github.com/Platoniq/decidim-bcnencomu/issues/16

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Barcelona en Comú