Release testing instructions: Storefront 4.2.0

Edit, reply and author icons are now displayed in comment list form. (#2066)

Before	After

1. Check and build this PR.
2. Add All Products block to the page.
3. See the color of add to cart button look as expected.
4. Save the page, see the style of the button look the same between editor and front end.
5. Use Customizer to change the text and background color of the button.
6. See the color apply to both front end and editor.

Stop theme defaults from overriding the Featured Item blocks text color (#2039)

Before	After

1. Activate the Storefront theme.
2. Add the Featured Product block to a page.
3. Select a product.
4. Confirm that the default color of the text inside is white (as seen in after screenshot above).
5. Change the color using the picker to a custom one (not included in the default palette).
6. The color of the text should change.
7. Repeat steps 2–6 with the Featured Category block.