Add a config to enable users to add attachments in comments

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

Our clients using Decidim for internal governance are using comments section a lot, to exchange good practices or share experiences.

In a lot of cases, they want to enable users to add attachments to their comments (photos, pdf, etc.).

Describe the solution you'd like

We could add a config flag, may be with Platoniq's Decidim awesome module to enable attachments in comments.

Describe alternatives you've considered

None

Funded by

Might be funded by CNRHR