Feature request: Please allow custom icons for Template Specs

It would be nice to be able to select icons for Template Specs to help distinguish them, especially when there are hundreds of them in a single Resource Group representing a large library of standard deployments for an org.

A quick-and-easy option would be to allow users to select from existing resource icons by referencing a resource type name. This way the spec icons would keep up with the "look and feel" changes of the Azure Portal over time.

A more flexible option would be to allow SVG files to be linked to the templates. Users could use icons from: https://docs.microsoft.com/en-us/azure/architecture/icons/ or any other source.

Start by clarifying whether icons should come from Azure resource type names, linked SVG files, or both. Review the Azure Portal icon conventions and the linked Azure architecture icons. Done means an agreed icon model with acceptance criteria for displaying and distinguishing Template Specs in large resource groups.

Written by the indexing model from the issue text.