Support IE11 (and other older browsers)

[jfilter]

Is your feature request related to a problem? Please describe.
Call me naive, but I really thought that Idyll would support IE11. It is still used by over 5% of desktop users.

Describe the solution you'd like
idyll build should make use of babel to transpile code that runs on IE11.

Describe alternatives you've considered
Not supporting older browsers. But then make it clear in the documentation.

[mathisonian]

Thanks for bringing this up @jfilter. I think the main culprits for the IE errors are coming from here where code is being dynamically generated, so it doesn't get transpiled.

At a quick glance there are two issues which will need to be updated to work with IE:

• Arrow functions
• Proxy objects

The handle the arrow functions we could just modify the existing code so it only uses the function keyword. Proxy objects are a little bit trickier, but there is a polyfill.

We could perhaps have users who want to support IE11 opt-in to including the polyfill?