Added circle-triangle edge arrow type

[kaino]

Issue type
Feature request

Description of new feature
Edge arrows as the combination of a triangle and a circle.

Motivation for new feature

In the last two years I've been using with great satisfaction cytoscape.js to manipulate graphs.
The original technology that I replaced with cytoscape, used the triangle + circle arrow style to represent the "owner" of a connection.
Since in my context such arrow style is part of a standard, I must keep it the same to avoid disruption or misunderstandings, so I would really like to have it as part of the cytoscape.js project.

Tests are passing, documentation + edges demo are updated accordingly.
Please let me know if anything is not clear, or in case of an issues with this pull request.

Thank you very much
Best Regards,
Paolo

[maxkfranz]

The PR looks great. My only suggestion would be to call the arrow type circle-triangle.

Other arrows that have multiple components, like triangle-tee, list the components starting from the end of the line and going inwards. For triangle-tee, the triangle is at the end of the line and the tee is inward:

For your shape, the circle is at the end of the line and the triangle is inward:

So circle-triangle may be a better fit.

If we support a new shape in future that has the triangle at the end and the circle going inwards, then the distinction between triangle-circle and circle-triangle will be important.

[kaino]

Hi @maxkfranz ,
thanks for reviewing this.
Actually, an open point for me was just the choice between 'triangle-circle' and 'circle-triangle'.
I've made the suggested changes on the PR, and tested it locally, everything should be fine.
Please let me know for any issues about the new commits.

Thanks again
Best Regards,
Paolo

[maxkfranz]

Great. The PR is merged in and the feature will be available in the 3.15.0 release at the beginning of May.

Thanks for the PR