fix(NcRichText) - keep newlines in rendered Markdown

[Antreesy]

☑️ Resolves

• Markdown eats newlines (Enter, Shift+Enter), because rendered <span/> element doesn't contain symbols, so it's height === 0
• For newline (several \n\n in a row) - we paste no-break space (unicode \u00A0) between to fill the line
• Also replaced strikethrough with inline code, as we don't support it yet

🖼️ Screenshots

🏚️ Before

Screencast.from.24.08.2023.14.27.11.webm

🏡 After

Screencast.from.24.08.2023.14.26.17.webm

🚧 Tasks

• ...

🏁 Checklist

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

[nickvergessen]

/backport to stable7

[DorraJaouad]

Tested 👍

[Pytal]

Adding label for auto-generated release notes

[dartcafe]

Not sure, if this matches the normal (official?) markdown bevahior:

• an empty line should create a paragraph <p></p> around the previous lines
• a simple line break <br> is created while adding two spaces at the end of a line (sometimes with a backslash or <br>)

Fair enough: Normal users will not be aware of the 'two spaces at the end of a line' thing. But at least the paragraph renderimg makes sense.

[Antreesy]

It's a workaround because of active rule white-space-collapse: collapse

Described by you behavior seems to match the current state:

[dartcafe]

The span tags are there for a reason? They look weird and unusual.

[Antreesy]

Thought the same, but it's a result of current parsing process. They probably could be removed, but with some deep changes I wouldn't like to touch for a moment