Make NavigationAccordion, SectionedAccordion, and PageLayout>sidebarTitle line up

[katydecorah]

This PR makes sure all sidebar items are lined up:

• Fixes uneven side spacing on NavigationAccordion, fixes NavigationAccordion has uneven spacing #253
• Adds the same padding to sidebarTitle in PageLayout
• Give SectionedAccordion same spacing

Current	Proposed

How to review

1. npm start
2. Navigate to /NavigationAccordion, /SectionedNavigation; /Feedback as a nice PageLayout example that you can preview

I also copied this component as a test in /mapbox-gl-js-docs:

1. Open /mapbox-gl-js-docs locally, pull down the nav-accordion-test branch.
2. yarn install
3. yarn start
4. Visit every /overview, /api, /examples to make sure all sidebar items are lined up.

QA Checklist

• No errors logged to console.
• Accessibility score in Chrome DevTools Audit/Lighthouse is 100% with Lighthouse version: 7.5.0. Tested a few pages and didn't get 100% due to NavigationDropdown, SectionedNavigation - Form elements do not have associated labels #248 and test-cases app having the docs Id baked in:
  • SectionedNavigation - 90
  • PageLayout - 90
  • NavigationAccordion - 91
• Component is accessible at mobile-size viewport.
• Component is accessible at tablet-size viewport.
• Component is accessible at laptop-size viewport.
• Component is accessible at big-monitor-size viewport.
• If applicable, create a PR in a site repo, copy the component, and test it. Push to staging and instruct the reviewer to test the component in-page.

Open the test cases app locally on:

• Chrome, no errors logged to console.
• Firefox, no errors logged to console.
• Safari, no errors logged to console.
• Edge, no errors logged to console.
• IE11, no errors logged to console.
• Mobile Safari, no errors logged to console.
• Android Chrome, no errors logged to console.

[colleenmcginnis]

🍪