Add an .editorconfig file

.editorconfig

@@ -0,0 +1,15 @@
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 4
+end_of_line = lf
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.{rb,sh,md,yaml},package.json]
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false