feat: enable disable form options

[giuliaghisini]

Is now possible to show or not some options in the column configuration from config:

config.settings["volto-editablefooter"] = {
    "options": { "socials": true, "newsletterSubscribe": true },
  };

[pnicolli]

LGTM, I only suggested an indentation fix in the README but the rest looks fine

[nzambello]

LGTM, I like it but I think the default values should be false, so it would be opt-in.
Socials are related to another addons, newsletter is not always present.

[nzambello]

We'll make a major due to the default change, it needs to be addressed

[nzambello]

@giuliaghisini se riesci documenta questa cosa come upgrade nel readme, così facciamo una major

[giuliaghisini]

@giuliaghisini se riesci documenta questa cosa come upgrade nel readme, così facciamo una major

fatto