Dx/add post compile hook

[pvbergen]

This PR introduces updating of styling profiles css when the iq_scss_compiler is run.

Works only in conjunction with iqual-ch/iq_barrio_helper#10, iqual-ch/iq_barrio#22, iqual-ch/iq_scss_compiler#5.

Open tasks:

• iq_stage_file_proxy is overriding compilation in local env
• Testing
• Review

[pvbergen]

Tested with GS1 locally:

• Styling profile changes were saved in the correct definitions file within sites/files/[STYLING_PROFILE]/iq_barrio/resources/sass/_definitions.scss and sass files of iq_custom and iq_barrio were copied and compiled
• Settings in /admin/appearance were correctly saved in themes/custom/iq_barrio/resources/sass/_definitions.scss
• Files were copied and compiled with drush iqsc:compile

Any other test cases?

[pvbergen]

Adjusting iq_stage_file_proxy in https://github.com/iqual-ch/iq_stage_file_proxy/pull/4/files; Moving alter hook to iq_scss_compiler