Add sitemap to Next.js (split ticket)

[rylew1]

Edit:

Repurpose this ticket into 2 tasks:

• Add a sitemap to Next.js
• Add pa11y-ci checks to the infra template (Add pa11y-ci accessibility checks against PR preview env template-infra#677)

Original description below:

What's the task?

Should we setup pa11y-ci https://github.com/pa11y/pa11y-ci for this project:

• possible defaults in .pa11yci.json:

  "defaults": {
    "timeout": 240000,
    "runners": ["axe"],
    "ignore": ["color-contrast"],
    "concurrency": 1,
    "chromeLaunchConfig": {
      "ignoreHTTPSErrors": true,
      "args": ["--disable-dev-shm-usage", "--no-sandbox"]
    }
  },

• some projects use a sitemap for the urls but we might need to finesse a possible url export of the data to get it into a format pa11y likes