tweak code formatting rules

* output as "json-stringify" (which is most similar to most files currently in the repository)
* add .editorconfig
* drop (now) superfluous pretter settings
* add npm commands to check code style

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 4
+
+[{data/deprecated.json,data/discarded.json,package.json,.package-lock.json}]
+indent_size = 2