Handle babel transpilation errors

[Nirajn2311]

Code -

mobile/mobile-app/lib/ui/views/learn/test_runner.dart

Line 71 in e4271d6

throw Exception('Babel transpilation failed: ${babelRes?.error}');

We need to handle this error by showing it to the user and put it in the console tab just like in the website. For now we're throwing it but the user is not aware that their code is incorrect.