Add Cumulative Score "steps" section to methodology page (#489)

* Step progress list
* Layout mostly done. Need to do intl() conversion but it's easier to understand the layout like this.
Will do intl in a different PR
* fix: `em` to `rem`
* Add basic snapshot unit test

client/src/components/scoreStepsList.test.tsx

@@ -0,0 +1,16 @@
+import * as React from 'react';
+import {render} from '@testing-library/react';
+import ScoreStepsList from './scoreStepsList';
+import {LocalizedComponent} from '../test/testHelpers';
+
+describe('rendering of the component', () => {
+  const {asFragment} = render(
+      <LocalizedComponent>
+        <ScoreStepsList/>
+      </LocalizedComponent>,
+  );
+
+  it('should match the snapshot of the MapIntroduction component', () => {
+    expect(asFragment()).toMatchSnapshot();
+  });
+});