Metric Distance Support

[binh-dam-ibigroup]

Description:

Fix #158
Supersedes #777

This PR adds a config parameter to display metric distances. Simply add to your config.yml:

units: metric

The default remains to show imperial units, so that existing implementations don't break.

PR Checklist:

• Does the code follow accessibility standards (WCAG 2.1 AA Compliant)? => MacOS Voice over correctly recognizes distance abbreviations. (have not tested other voice tech)
• Are all languages supported (Internationalization/Localization)?
• Are appropriate Typescript types implemented?

Screenshots:

[miles-grant-ibigroup]

@amenk You might be interested in this!