Handle users with unsupported browsers

[Grsmto]

Related to #12 and @josepmc suggestion:

React is supported until IE9 so the solution I would recommend:

• Add a super simple <noscript/> for JS disabled users.
• Implement React error boundaries and have an "error" page (can look like the 404) for any user that encounter JS error (IE9 up to whatever version we support). We usually bind it to Sentry (once we'll have that setup) to send the error there for tracking as well.