Add .editorconfig - default indentation for text editors and github

https://editorconfig.org/

.editorconfig

@@ -0,0 +1,16 @@
+# EditorConfig is awesome: http://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+insert_final_newline = true
+indent_style = tab
+indent_size = 4
+
+[*.yml]
+indent_style = space
+indent_size = 2
+
+[*.{txt,md}]
+charset = utf-8