ICON_BASE_SOURCE is always required

[guilhermejcgois]

Is your feature request related to a problem? Please describe.
Writing tests for components that use gor-icon always requires a value for said token

Describe the solution you'd like
Have a default value for it and not break the DI (see #114 )

Describe alternatives you've considered
Set a default value and use @SkipSelf in IconComponent

Additional context
Add any other context or screenshots about the feature request here.

QUESTION FOR GORILA TEAM
Is a new or old component?

[ ] new component [x] old component

Is this component used by more than 2 projects?

[x] yes [ ] no