Add capability for multiple custom connectors to be connected to edges

[ktsao565]

This is an initial PR to get some eyes on the overall approach. Additional unit tests and integ tests are in progress, but I wanted to initiate the initial review on the high level changes.

Issue #, if available: https://github.com/awslabs/diagram-maker/issues/67

Description of changes:

• Add capability for edges to connect to individual custom connectors
• Allow consumer to configure the position of custom connectors

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[sameergoyal]

Just checking if there are plans to address the comments and merge this one in?

[diehbria]

@sameergoyal reached out to author who confirmed they still plan on completing this PR

[matr369]

any updates?

[tracy-french]

@matr369 Change has been merged.