Add .editorconfig for consistent code formatting

always useful to have :-)

.editorconfig

@@ -0,0 +1,16 @@
+# https://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 2
+indent_style = space
+trim_trailing_whitespace = true
+
+[*.js]
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false