Hard coded notification URL needs to become configurable

[rsdoiel]

Hard coded notification URL needs to become configurable as a top level item in cold_reports.yaml. There are a few related values hard coded and likewise they should be made configurable for the reports runner and UI.

[rsdoiel]

I've added a baseUrl value to the config.ts interfaces. These need to propagate through. It'd be helpful to have this configurable via YAML or the environment.

When I get closer to a 0.1.0 release a code review needs to happen where we collect these types of hard coded values and make them configurable but also have sensible defaults.