Add say-content styling to all treatment content (Fixes sub/superscript)

[x-m-el]

Overview

Some preview content in GN did not show the same as content on other places. The problem comes from a missing class say-content.
This adds the same styling of say-content to c-template-content--treatment, which contains this content where the styling was missing.

connected issues and PRs:

https://binnenland.atlassian.net/browse/GN-4210
lblod/ember-rdfa-editor#989

Setup

npm link the editor
npm link @lblod/ember-rdfa-editor in this repo

How to test/reproduce

See ticket for a specific example. The easiest is to add some superscript/subscript to an agenda item and see that this is rendered correctly on any place an agenda item is rendered.

Challenges/uncertainties

I wanted to avoid this solution as it is a bit hacky (and needs an editor change)
However:

• changing the preview means changing the notulen-prepublish-service template, which is something we don't want to touch. It might also mean that this extra class would be added to a published document. In principle c-template-content--treatment is enough as a class to identify the treatment part in the template. No need to add another class.
• could also add the class say-content in the frontend somehow.
  • add say-content via queries in components, but there are many components showing this preview.
  • add say-content class via queries in a special getter for treatment (e.g. previewContent). But this means parsing the html before it is rendered. This might be better, but for big documents this could take some time and the css fix is quite easy to understand.