Handle Adding Vertical Lanes

[sombrek]

Closes #2086

• I fixed come CRLF line endings in a separate commit.
• I did not add tests for undefined lanes, since special handling for such lanes already exists and is tested (IsHorizontalFixSpec).

[nikku]

As we're adding more features in the context of vertical lanes: I think it makes sense to add to dedicated "vertical" examples to our modeler and viewer specs. These are the ones we usually use for end-to-end (integration) testing.

[barmac]

Thank you for your contribution.

I've added a vertical collaboration example via 1cf81d2

In this PR, the nested lane is still not handled correctly:

Screen.Recording.2024-01-30.at.10.20.35.mov

We may consider to flip the icons in the future, but it's not required to merge this.

[barmac]

As a follow-up, I created an issue for the hit box: #2093

[sombrek]

@barmac Thanks for the additional test and the follow-up.

In this PR, the nested lane is still not handled correctly:

Honestly, until now I didn't think of splitting lanes as adding nested ones, so I didn't work on splitting yet. But I see your point now. Would you like me to include splitting in this PR (may take two weeks) or can I do it in a separate one?

[barmac]

It's OK to have it as a separate PR then. I will merge this.

[barmac]

I checked the issue again. You mentioned splitting there: #2086 (comment) So I won't close it but rather keep a link in this PR.

[barmac]

Released via #2094