update eslint `jsx-a11y/anchor-is-valid` config 

the current config for `jsx-a11y/anchor-is-valid` dings us when a react router `Link` component doesn't have an `href` attribute, even if it has a `to` attribute.

The following rule update covers this use case:

`/* eslint 'jsx-a11y/anchor-is-valid':
  ['error', {
    components: ['Link'],
    specialLink: ['to'],
    aspects: ['noHref', 'invalidHref', 'preferButton'],
  }] */`