feat(NcRichText) add support of GFM (extended markdown)

[Antreesy]

☑️ Resolves

• Add package remark-gfm for further support of:
  • autolink literals
  • footnotes ??
  • strikethrough ~~
  • tables -- | --
  • tasklists - [ ] - [x]
• parsed text was hacked to insert non-breaking space between each two new lines. Thus span which rendered for a new line, have both width and height parameters, and is visible in the window

🖼️ Screenshots

markdown-checkboxes.webm

In Talk messages:

🚧 Tasks

• ...

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable

[susnux]

One thing I am not sure about is whether we want to different Markdown flavors, as this can be quite confusing.
So on the one side we would have the text and collectives apps running on CommonMark + Extensions and on the other side Talk.

Maybe we should make sure NcRichText and Text supports the same Markdown dialect?

[Antreesy]

Maybe we should make sure NcRichText and Text supports the same Markdown dialect?

That could be the best way to do that.

[Antreesy]

Link to documentation:

• Github FM: https://github.github.com/gfm/
• CommonMark Spec: https://spec.commonmark.org/

So, GFM is based on CMS, including such extensions as autolink, strikethrough, tables and tasklists. I see they're activated in Text app as well: https://github.com/nextcloud/text/blob/cd39a0decac0a6f003d4bddff22faa70c3e71ae5/src/markdownit/index.js#L13-L16

From that point, flavor would be the same, although we might need to align syntax for some extensions (and not sure this make sense for the tables, as Text has injected table editor, which would be an overkill for Talk input)

To ensure we're supporting the same syntax, we could try to base NcRichText tests on https://spec.commonmark.org/0.30/spec.json somehow, but I don't think it's needed, as libraries based on the same specs

[Antreesy]

Because of using some React functionality at master branch to create nodes, I had troubles with passing an event from rendered checkbox to parent. Will make another attempt

Apart from it, a basic extended markdown is working and evem possible to backport for master release, although I don't know, if it's considered as breaking change or not (original behavior was untouched, this goes under new functionality)

[ShGKme]

Cool, seems to work fine. Some comments

[Antreesy]

Aj, we forgot to put it into the 8.5.0 changelog 🙈

[Pytal]

🙈 sorry, looks like this one was excluded by our config

nextcloud-vue/.github/release.yml

Line 11 in 99a7c57

- dependencies

because of the dependencies label