Step 2 — Set Babel’s IE target from 9 to 11

[sampi]

We don't need to support IE8 & IE9 anymore…

This is how you can modify babel's target settings, not just IE ;)

The same way it was possible to change the webpack config, we're going to do just that to babel.

Files sizes remain the same because there are no 'fancy' methods used in the preact code so it compiles just the same on IE9 and IE11.