Upgrade Pa11y - ERR_HTTP2_PROTOCOL_ERROR

[geoffroy-noel-ddh]

We use Pa11y version 6. We should upgrade to 8 so we get newer version of puppeteer & axe-core.

This shouldn't require much change in our code (see migration page on Pa11y).

However there's an issue with Browser connection to some sites (e.g. thornton.kdl.kcl.ac.uk) after the upgrade to 8.

~/src/prj/webval$ node docs/evaluate.js thornton 
Project Alice Thornton https://thornton.kdl.kcl.ac.uk
  PA11Y /
net::ERR_HTTP2_PROTOCOL_ERROR at https://thornton.kdl.kcl.ac.uk/

As suggested by other people with the same problem I've tried to set the user agent in the Pa11y config, but that doesn't work.

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A second problem with the upgrade is to ensure that the github workflow to evaluate projects on demand still works with npm, puppeteer, etc.