Update Pa11y Config for Node Pattern Lab 3

[jryanconklin]

Issue

The default config for pa11y is no longer compatible with Node PL 3.

Analysis

See this PR on the update to resolve: pattern-lab/patternlab-node#1035

const {
  patternPaths,
  navItems,
  // eslint-disable-next-line import/no-unresolved
} = require('../dist/app-node-pl/pl/styleguide/data/patternlab-data.cjs.js');

This PR should account for documenting how to fix as well as tracking the Pattern Lab PR above to see if it's merged. If merged, we don't need to patch Particle. Else, we should create the patch file per docs/patches.md

Confirmation

As a developer, I can run pa11y tests on my Particle.

[jhedstrom]

This fix should also add pa11y-ci back to the devDependencies section of package.json file, as it is missing at this time.

[jryanconklin]

@jhedstrom We don't turn on pally-ci by default on Particle. It's up to the project to enable it considering the size of the Chromium download.