chore(docs): use raw link for message images #1835

Job	Run time
build-and-test (16.x, macos-latest)	5m 24s
build-and-test (16.x, ubuntu-latest)	7m 52s
build-and-test (16.x, windows-latest)	16m 39s
build-and-test (18.x, macos-latest)	11m 2s
build-and-test (18.x, ubuntu-latest)	12m 15s
build-and-test (18.x, windows-latest)	24m 10s
build-and-test (20.x, macos-latest)	6m 3s
build-and-test (20.x, ubuntu-latest)	9m 8s
build-and-test (20.x, windows-latest)	13m 49s
	1h 46m 22s

Provide feedback