This config file is used by codefactor.io and can be used to override
some of the default settings. The default config has been obtained from:
https://github.com/codefactor-io/default-configs/blob/master/.eslintrc.json

Previously, this setting led to a lot of false positives in out
controller scripts, e.g.:

    'group' is defined but never used.
    Found in res\controllers\KANE_QuNeo_scripts.js:1120
    KANE_QuNeo.scrollPlaylist = function (channel, control, value, status, group) {

JS coding conventions can be found at:
https://www.mixxx.org/wiki/doku.php/contributing_mappings#coding_conventions_for_javascript

The .eslintrc.yaml for novation-launchpad has issues with recent
versions of eslint and requires installation of custom npm packages.

    $ eslint .

    Oops! Something went wrong! :(

    ESLint: 6.8.0.

    ESLint couldn't find the config "standard" to extend from. Please check that the name of the config is correct.

    The config "standard" was referenced from the config file in "/data/jan/Projects/mixxx/res/controllers/novation-launchpad/.eslintrc.yaml".

    If you still have problems, please stop by https://gitter.im/eslint/eslint to chat with the team.

These shouldn't cause a lot of linter issues in our existing codebase
(if any). There's no reason why they shouldn't be enabled IMHO.

Although Promises aren't support by Qt Script anyway, some scripts in
the res/controllers directory are using Promises anyway (i.e. the Novation
Launchpad scripts). So in any case it doesn't hurt to enable this rule.

…parens

Add eslintrc for CodeFactor.io

.eslintrc.json: Add more rules regarding spacing