PastVu
Define the list of supported browsers through a browserslist configuration.
Instead of having a static list of unsupported browsers https://github.com/PastVu/pastvu/blob/master/config/browsers.config.js#L5-L13, which does not get updated regularly, define the list of supported browsers through a browserslist configuration.
Default configuration (> 0.5%, last 2 versions, Firefox ESR, not dead) is reasonable enough, although when implementing this, check Google Analytics stats (or request this info from maintainers) to see if those requirements may need to be eased off.
Babel is supposed to respect browserlist config already (needs investigation, it might be more complex than how it looks with regard to polyfills in particular), changes will be required in the area where user agent is validated and user is directed to "non supported browser" page. Packages browserslist-useragent and browserslist-useragent-regexp may come to use here.
