Add an .eslintrc so editors can lint

[citelao]

I got linting to work by adding a basic .eslintrc file:

{
"extends": "./node_modules/electrode-archetype-react-app/config/eslint/.eslintrc-react"
}

(this, of course, could be configured to use the other eslint files present)

With Pull 35 in the app archetype, it will be possible for developers to override electrode defaults rules.

[citelao]

I'm not sure this fixes the issue; there's still no eslintrc in any directory.