Enable editorconfig to enforce formatting, make sure build-and-serve works

.editorconfig

@@ -0,0 +1,13 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = tab
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+# YAML requires indentation with spaces instead of tabs.
+[*.{yml,yaml}]
+indent_style = space
+indent_size = 2