Add editorconfig

.editorconfig

@@ -0,0 +1,20 @@
+# editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.{rb,coffee,css,scss}]
+max_line_length = 80
+
+[*.js]
+max_line_length = 120