fix(NcRichText) - don't populate a first newline to properly parse blockqoute tags

[Antreesy]

☑️ Resolves

• Regression from fix(NcRichText) - keep newlines in rendered Markdown  #4461
• Condition for <blockqoute/> was broken, as at least one line after it should be empty
• Added Cypress tests based on https://www.markdownguide.org/basic-syntax and https://github.com/nextcloud-deps/CDMarkdownKit/tree/master/CDMarkdownKitTests

🖼️ Screenshots

🏚️ Before	🏡 After

🚧 Tasks

• Code review
• Manual testing

🏁 Checklist

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

[nickvergessen]

Fixes the bug in talk

[Antreesy]

Rebased onto master, added cypress tests

[DorraJaouad]

The patterns seem right :) . I am just not sure if condensing each two new lines having ">" each into one line is intentional ( if there is n, an odd number of ">", then it is (n+1)/2 new lines) .
Tested and it works as expected otherwise .

[Antreesy]

I am just not sure if condensing each two new lines having ">" each into one line is intentional

That's for empty lines in quote notation:

> quote line 1
>
> line 3