Canvis a "See the full content of comments in Notifications"

Ref. PWA11.3

NOTE: this feature is from a big development. See PWA discussion at GitHub.

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

As a registered participant who is following content in Decidim, when there is a new comment notification, it only shows that “There was a new comment”. For instance, “There is a new comment by Decidim Product @product in Possibility to configure default sorting for proposals.”.

Describe the solution you’d like

I want to have the full text of the comment in the notification itself. For instance “There is a new comment by Decidim Product @product in Possibility to configure default sorting for proposals: Hi there! This is the proposal we have agreed on in @product: add all the options for sorting proposals, plus the “By default” option, which maintains the current behavior. We also add contextual help explaining it. See mockup here: https://imgur.com/a/0AnldpR”

Acceptance criteria

• Given that I’m a participant with a new comment notification,
  When I go to my notifications page
  Then I can read the full comment on the notifications page.