feat(wdio): add screenshot, URL a11y issues output from @sa11y/wdio

[mohanraj-r]

Create a template for a11y issues output from webdriver tests which includes additional info such as screenshot and URL of page tested. Save screenshot locally (to a temp dir) and include path to image. Reuse (and simplify) existing template from Java webdriver tests : https://github.com/mohanraj-r/sa11y/tree/WIP/add_template_formatter