Enable soft line break for markdown.

[nilsreichardt]

Description

Since last summer, it's possible to enable soft line breaks (flutter/packages#437). Therefore, no \ is required anymore.

I think adding the support for soft line break is the better solution instead of \ because it's completely intuitive and for nearly every user it's new that you can break a line with \.

Prevents also confusions like https://discord.com/channels/545668860859252746/616181222577668106/956087823692361768

Before	After

Text:

Guten Tag,
was geht.
asdf


asdfasf


hallo\
safdfs

[github-actions]

Visit the preview URL for this PR (updated for commit a1fee49):

https://sharezone-test--pr139-markdown-soft-line-b-l91ioghy.web.app

_{(expires Thu, 31 Mar 2022 19:47:44 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

[Jonas-Sander]

@nilsreichardt Bei den Termindetails ist das scheinbar noch nicht aktiviert

[Jonas-Sander]

See comment above.
LGTM for everything else.

[nilsreichardt]

@nilsreichardt Bei den Termindetails ist das scheinbar noch nicht aktiviert

Good catch!