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

.prettierignore

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

prettier.config.js

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2017-present Arctic Ice Studio <[email protected]>
+ * Copyright (C) 2017-present Sven Greb <[email protected]>
+ *
+ * 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 <[email protected]>
+ * @author Sven Greb <[email protected]>
+ * @see https://prettier.io/docs/en/configuration.html
+ */
+
+module.exports = {
+  printWidth: 120
+};