cdk proposal: framework for rich text editors ("draftjs" for angular)

tl;dr https://draftjs.org/ for angular

I've been searching the internets and there is nothing that comes even close to draftjs, which is built on top and requires react. What does it do? It solves most of the [contenteditable issues](https://medium.engineering/why-contenteditable-is-terrible-122d8a40e480) and provides api for people to build their own rich text editors on top of it.

Rich text editor doesn't necessarily mean WYSIWYG textarea, it can help with anything from mentions, hashtags to replacing text emoticons with images etc.


Some of the most popular draftjs plugins can be found [here](https://www.draft-js-plugins.com/) and [here](https://github.com/nikgraf/awesome-draft-js), it should give you an idea what can be done with it.

worth reading:
- https://code.facebook.com/posts/1684092755205505/facebook-open-sources-rich-text-editor-framework-draft-js/
- https://medium.com/@rajaraodv/why-draft-js-and-why-you-should-contribute-460c4a69e6c8
- https://medium.com/@rajaraodv/how-draft-js-represents-rich-text-data-eeabb5f25cf2

I think this could be a great fit for CDK, given that you are eventually planning on creating WYSIWYG anyway.. what do you think?

@jelbourn @mmalerba @kara @andrewseguin @DevVersion @crisbeto

Beginne mit der Durchsicht der im Issue beschriebenen Draft.js-Ressourcen und des Angular-CDK-Kontexts, einschließlich der verlinkten Verweise auf Editor und Plugins. Definiere vor der Implementierung die vorgeschlagene Angular-Integration, den API-Umfang und die Abnahmekriterien; die Arbeit ist abgeschlossen, wenn das Framework-Design und die Passung zum Projekt abgestimmt sind.

Vom Indexierungsmodell aus dem Issue-Text verfasst.