Update stylelint (#3042)

1. Update `stylelint` dependencies
- As of stylelint v15, we do not need `stylelint-config-prettier`
anymore:
https://github.com/prettier/stylelint-config-prettier/releases/tag/v9.0.5
2. Switch to `stylelint-config-standard`:
`stylelint-prettier/recommended` has not been updated for a long time
and still needs the old `stylelint-config-prettier`
3. Handle new `stylelint` issues

tests/e2e/modules/clock_spec.js

@@ -103,7 +103,7 @@ describe("Clock module", () => {
 		});
 
 		it("should show the analog clock face", async () => {
-			const elem = helpers.waitForElement(".clockCircle");
+			const elem = helpers.waitForElement(".clock-circle");
 			expect(elem).not.toBe(null);
 		});
 	});