config.json parsing issues seem to be swallowed

[prydonius]

#891 fixed a syntax error in the config.json file that was causing deployments to fail, but we didn't easily figure out that it was due to the syntax error in that file. We should easily be able to detect parsing errors for that file and bubble them up so they are more noticeable. See also https://kubernetes.slack.com/archives/C9D3TSUG4/p1545178666065400.

Looks to me like axios is swallowing the error up: https://github.com/kubeapps/kubeapps/blob/490b316eb9df7d070fef7442fc5736d60d018175/dashboard/src/shared/Config.ts#L12