Use eslint-config-arcticicestudio preset and override conflicting rules

The used preset eslint-config-arcticicestudio (1) implements the Arctic
Ice Studio JavaScript Style (2). It it built on top of
eslint-config-arcticicestudio-base (3) and includes support for rules of
the following plugins:

- eslint-plugin-import (4)
- eslint-plugin-jsx-a11y (5)
- eslint-plugin-react (6)

>> Disabled rules

Due to compatibility problems and message noise the `no-confusing-arrow`
rule has been disabled. It can be re-enabled again when the used preset
handles the problem or disables the rule too.

Also to suppress errors in the future with Gatsby the
`import/no-extraneous-dependencies` has been overridden (still error
`level`) by adding the `devDependencies` option and add the exception
for `./.gatsby/**/*.js`. This allows to use development dependencies in
Gatsby configuration files without linting errors since these are
necessary and some will be provided by Gatsby itself without being
explicitly added to the `package.json`.

References:

  (1) https://github.com/arcticicestudio/eslint-config-arcticicestudio
  (2) https://arcticicestudio.github.io/styleguide-javascript
  (3) https://github.com/arcticicestudio/eslint-config-arcticicestudio-base

  (4) https://github.com/benmosher/eslint-plugin-import
  (5) https://github.com/evcohen/eslint-plugin-jsx-a11y
  (6) https://github.com/yannickcr/eslint-plugin-react

GH-15

.eslintrc.js

@@ -16,8 +16,14 @@
  */
 
 module.exports = {
+  extends: "arcticicestudio",
   env: {
     browser: true,
     node: true
+  },
+  rules: {
+    "no-confusing-arrow": "off",
+    /* Suppress errors when importing development dependencies */
+    "import/no-extraneous-dependencies": ["error", { devDependencies: ["./.gatsby/**/*.js"] }]
   }
 };