Establish patterns or objects for using custom node icons

[jsoconno]

Is your feature request related to a problem? Please describe.
As a user, I am not able to bring custom icons to my diagrams.

Describe the solution you'd like
We should create a new object type that is like Node, but allows users to bring custom icons from their local setup. This would allow us to focus on icons we think are generally useful and tie back to a Terraform configuration while others can bring their own. This also gives us an answer for people who want icons we would not generally support or that are not critical path to implement.

Describe alternatives you've considered
Just requiring all icons to be directly contributed to architectures. While i think in some cases we will want to do this, if the goal is to make these diagrams deployable, it might make more sense to focus on the big cloud providers and terraform configurations for those and let others bring their own.

Additional context
None.