ember-a11y-testing updates and simplification

[scalvert]

This addon has largely been left untouched since its initial creation. There have been a number of default Ember blueprint updates (outside of this repo), which were hard to pull in due to it being so out-of-date.

In addition to this, the @ember/test-helpers addon, which is one of the underpinnings of Ember's testing system, had evolved to include some new and useful APIs that could positively impact the direction of this addon. More specifically, the new hooks API could be leveraged to automatically wire up accessibility audits in a hands-off manner, allowing apps and addons to progress their code to being more accessible.

Based on the above, there are a number of updates to this addon that are proposed:

• Ensure it's up-to-date with the latest blueprint. (Regenerates lockfile to address issue with fsevents version #181, Unpinning dependencies to allow for easier blueprint upgrades #182, Attempting to fix renovate so it won't open pin dependency PRs #187, Updating to [email protected] blueprint #190)
• Convert to TypeScript. Adding TS allows the APIs to be cleaned up and validated, in terms of this public interfaces. (Add support for migrating to TypeScript #184, Converting utils to TS to fix compile time errors #204)
• Update linting. (Update linting configuration to work with TypeScript (+Prettier) #188)
• Converting to use Github actions vs. Travis (faster CI execution). (Convert to github actions #192, Updates build status badge to use github actions #193)
• Convert a11yAudit failure to use throw vs. Ember.assert. (Converts the Ember.assert usage to throwing error for failing tests #201)
• Implement new setupGlobalA11yHooks API, which leverages the new hooks API in @ember/test-helpers. (Issue: [New API] Add setupGlobalA11yHooks helper #186, PR: Implements setupGlobalA11yHooks helper #200)
• Drop support for moduleForAcceptance. This API is deprecated. (Drop support for moduleForAcceptance #199)
• Deprecate a11yAuditIf (Deprecate a11yAuditIf #203)
• Remove non-test related components and infrastructure (Remove audit components in favor of industry standard tools #205)
• Implement new reporter system, allowing for the custom reporting of violations (Adds custom reporter capability #210)
• Update README with all API and functional changes (Updates the README and ensures correct jsdocs are present for all public APIs #215)

Once the above are completed this addon should be in a stable state, and a new major version should be released.

[scalvert]

All of the above have been merged, so closing this.