a11y: HTML needs `lang` attribute and value

[iamjolly]

Description:

The language of each page must be set so that text is presented correctly for assistive technologies and conventional browsers/user agents.

WCAG SC

Success Criterion 3.1.1 Language of Page (Level A): The default human language of each Web page can be programmatically determined.

Location of code:

/app/views/layouts/application.html.erb, line 2

Recommended fix:

Apply lang="en" to the html element in the application layout view as well as anywhere the html element may be rendered from.