HorizontalRule: fix setHorizontalRule putting cursor at non-text positions

[bdbch]

Please describe your changes

This PR fixes an issue with the setHorizontalRule function placing the selection at non-text positions (for example doc) after inserting a HorizontalRule node.

How did you accomplish your changes

I modified the insert positions of the functions and added a small part of code to determine the next text-node which the cursor can be placed in.

How have you tested your changes

Locally with the HorizontalRule demo.

How can we verify your changes

See above

Remarks

Nothing

Checklist

• The changes are not breaking the editor
• Added tests where possible
• Followed the guidelines
• Fixed linting issues

Related issues

fixes #3003

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[rfgamaral]

@bdbch I'm finding that this change isn't working that well:

firefox_mjKS0cpkoG.mp4

I'm also having a strange issue in your Typist editor:

firefox_gLIsARPgGI.mp4

For some reason, it's trying to insert an hashtag suggestion. This could either be a problem on our side, or a related issue to the bug above.

For now - and even before upgrading tiptap to v2.1 - we've been using a custom horizontal rule extension, with this patch, that seems to work much better.

Would be nice to remove this work around from our side, but unfortunately, this behaviour is still buggy on tiptap.

[svenadlung]

@rfgamaral just to be sure: this got fixed for you with 2.1.6, did it?