Update Node and BackstopJS

[rmccar]

What is the context of this PR?

Fixes: ONSdigital/design-team#60

This solves the warning we are seeing in the logs when our VR tests are run.

I have updated a few dependecies including node and backstopjs.

@babel/preset-env has also been updated which will fix the caniuse lite warning when running yarn start

Also codecov has been removed because we no longer use it.

There are also a few docs and formatting changes

How to review this PR

• Tests pass
• Changes make sense
• Check that the warning in the installing dependancies step of the VR tests action is now gone
• Check that the caniuse lite warning is now gone when running yarn start

Checklist

This needs to be completed by the person raising the PR.

• I have selected the correct Assignee
• I have linked the correct Issue

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[rmccar]

Most of these changes will be fixed in another PR. We should raise a seperate PR to look into the issues around backstop