Prettier (#55)

* Install `prettier`

Installed the main `prettier` (1) NPM package.

References:
  (1) npmjs.com/package/prettier

Epic: GH-33
Depends on GH-47 GH-49
GH-37

<--------------------------------------------------------------------->

* Implement Prettier configuration and ignore pattern file

This is one of the main features of Prettier: It already provides the
best and recommended style configurations of-out-the-box.
The only option that has been changed is the print width (1). It is set
to `80` by default which not up-to-date for modern screens (might only
be relevant when working in terminals only like e.g. with Vim). It is
now set to `120` used by all of Arctic Ice Studio's style guides.
The `prettier.config.js` configuration file is placed in the project
root as well as the `.prettierignore` file that defines ignore pattern.

References:
  (1) prettier.io/docs/en/options.html#print-width

Epic: GH-33
Depends on GH-47 GH-49
GH-37


* Implement NPM `format:pretty` script/task for Prettier

To allow to format all sources the `format:pretty` NPM script/task has
been added as well as the `format` script/task to run all tasks of the
formatting workflow.

Epic: GH-33
Depends on GH-47 GH-49
Resolves GH-37

.prettierignore

@@ -0,0 +1,8 @@
+# Copyright (C) 2017-present Arctic Ice Studio <development@arcticicestudio.com>
+# Copyright (C) 2017-present Sven Greb <development@svengreb.de>
+#
+# Project:    snowsaw
+# Repository: https://github.com/arcticicestudio/snowsaw
+# License:    MIT
+
+**/node_modules/*

package.json

@@ -26,11 +26,14 @@
     "arcticicestudio"
   ],
   "scripts": {
-    "lint": "npm-run-all lint:*",
-    "lint:md": "remark --no-stdout . \".github/**/*.md\""
+    "format:pretty": "prettier --write \"./**/*.{js,json,md,yml}\"",
+    "format": "npm-run-all format:pretty",
+    "lint:md": "remark --no-stdout . \".github/**/*.md\"",
+    "lint": "npm-run-all lint:*"
   },
   "devDependencies": {
     "npm-run-all": "4.1.5",
+    "prettier": "1.18.2",
     "remark-cli": "6.0.1",
     "remark-preset-lint-arcticicestudio": ">=0.3.0 <1.0.0"
   },

prettier.config.js

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2017-present Arctic Ice Studio <development@arcticicestudio.com>
+ * Copyright (C) 2017-present Sven Greb <development@svengreb.de>
+ *
+ * Project:    snowsaw
+ * Repository: https://github.com/arcticicestudio/snowsaw
+ * License:    MIT
+ * References:
+ *   https://prettier.io/docs/en/configuration.html
+ *   https://prettier.io/docs/en/options.html
+ */
+
+/**
+ * @file The Prettier configuration.
+ * @author Arctic Ice Studio <development@arcticicestudio.com>
+ * @author Sven Greb <development@svengreb.de>
+ * @see https://prettier.io/docs/en/configuration.html
+ */
+
+module.exports = {
+  printWidth: 120
+};