add editorconfig

.editorconfig

@@ -0,0 +1,21 @@
+# editorconfig.org
+root = true
+
+[*]
+indent_style = tab
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.{html,ejs,css,sass,scss,js,yml}]
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[{package.json,.travis.yml}]
+indent_style = space
+indent_size = 2