tooling(style): add .editorconfig and change formatter settings

editorconfig contains entries for yml and dart now
the formatter will no longer collapse multiline code splits (like class
constructors), where the last entry has a trailing comma

.editorconfig

@@ -0,0 +1,17 @@
+# EditorConfig is awesome: https://editorconfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = false
+trim_trailing_whitespace = true
+
+[*.dart]
+indent_style = space
+indent_size = 2
+
+[*.yaml,*.yml]
+indent_style = space
+indent_size = 2