Allow changing light and dark text color of headings #1140

Job	Run time
jest (pageflow, package)	2m 41s
jest (pageflow-paged, entry_types/paged/packages/pageflow-paged)	1m 23s
jest (pageflow-paged-react, entry_types/paged/packages/pageflow-paged-react)	2m 0s
jest (pageflow-scrolled, entry_types/scrolled/package)	2m 40s
rspec (pageflow, ., bin/rspec --tag ~js, true)	6m 15s
rspec (pageflow, ., bin/rspec-with-retry --tag js)	5m 23s
rspec (pageflow_paged, entry_types/paged, pageflow_paged, bin/rspec)	3m 44s
rspec (pageflow_scrolled, entry_types/scrolled, pageflow_scrolled, bin/rspec --tag ~js)	4m 47s
rspec (pageflow_scrolled, entry_types/scrolled, pageflow_scrolled, bin/rspec-with-retry-on-timeou...	6m 26s
trigger-edge-build	0s
	35m 19s

Provide feedback