Add editor config and linter

.editorconfig

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+# This file is for unifying the coding style for different editors and IDEs
+# editorconfig.org
+
+# WordPress Coding Standards
+# http://make.wordpress.org/core/handbook/coding-standards/
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 4
+tab_width = 4
+indent_style = tab
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.txt]
+trim_trailing_whitespace = false
+
+[*.{md,json,yml,js}]
+indent_style = space
+indent_size = 2

.eslintrc.yml

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+env:
+  browser: true
+  commonjs: true
+  es6: true
+  node: true
+parserOptions:
+  sourceType: module
+rules:
+  indent:
+    - error
+    - 2
+  linebreak-style:
+    - error
+    - unix
+  quotes:
+    - error
+    - single
+  semi:
+    - error
+    - always