Add editorconfig file (#246)

* Add editorconfig file

It's a cross-editor compatible config file that defines certain editor
behaviour (e.g. adding/removing newline at end of file)

It is supported by major editors like Visual Studio (Code) and by
version control  providers like GitHub.

Should end the constant adding/removing of final newline in PRs

* More settings

- unicode by default
- trim newlines
- use tabs for indentation (ugh)

.editorconfig

@@ -0,0 +1,11 @@
+# For more info on `.editorconfig` file see https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Newline ending every file
+[*]
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+indent_style = tab