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

analysis_options.yaml

@@ -24,5 +24,10 @@ linter:
     # avoid_print: false  # Uncomment to disable the `avoid_print` rule
     # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
 
+formatter:
+  # collapseable entries, e.g. classes, don't get put into a single line if
+  # there is a trailing comma behind the last entry
+  trailing_commas: preserve
+
 # Additional information about this file can be found at
-# https://dart.dev/guides/language/analysis-options
+# https://dart.dev/guides/language/analysis-options