add editorconfig

.editorconfig

@@ -0,0 +1,17 @@
+# Cross-editor formatting rules
+# see: https://editorconfig.org
+
+root = true
+
+[*]
+charset=utf-8
+end_of_line=lf
+insert_final_newline=true
+trim_trailing_whitespace=true
+
+[*.lua]
+indent_size=4
+indent_style=space
+
+[*.md]
+trim_trailing_whitespace=false