Instead of using `eslint-plugin-json` for linting JSON files,
`prettier` is now used. `prettier` is capable of detecting and
correcting more problems than `eslint-plugin-json` can, such as
indentation.
All JSON files have been run through `prettier`. The changes are all
superficial.
This tests the `personal_sign` method using the test dapp. This test
reflects part of the `confirm-sig-requests` integration test, which
tests the confirmation of a `personal_sign` signature request.
A `data-testid` prop was added to the 'Sign' button on the signature
request confirmation page, to make it easier to select the 'Sign'
button reliably.
