[Bug 1015334] Workaround mapbox multiple-city-with-same-name issue, and cosmetic/l10n tweaks.
[docs] Update Contributing Section in docs.

* Add testing details
* Add linting step
* Add CONTRIBUTING.md
Merge pull request #965 from glogiotatidis/docs-contributing

[docs] Update Contributing Section in docs.
Merge pull request #962 from Sancus/geofixes

[Bug 1015334] Workaround mapbox multiple-city-with-same-name issue, and cosmetic/l10n tweaks.
Location fixed - NOTREADY