update list of supported stylelint rules on README

Author: morishitter

README.md

@@ -331,6 +331,7 @@ stylefmt supports the following stylelint rules:
 - [block-opening-brace-space-after](https://github.com/stylelint/stylelint/tree/master/src/rules/block-opening-brace-space-after)
 - [block-opening-brace-space-before](https://github.com/stylelint/stylelint/tree/master/src/rules/block-opening-brace-space-before)
 - [color-hex-case](https://github.com/stylelint/stylelint/tree/master/src/rules/color-hex-case)
+- [declaration-block-properties-order](https://github.com/stylelint/stylelint/tree/master/src/rules/declaration-block-properties-order)
 - [declaration-colon-space-after](https://github.com/stylelint/stylelint/tree/master/src/rules/declaration-colon-space-after)
 - [declaration-colon-space-before](https://github.com/stylelint/stylelint/tree/master/src/rules/declaration-colon-space-before)
 - [indentation](https://github.com/stylelint/stylelint/tree/master/src/rules/indentation)