Add nesting for @support

Author: jacobcassidy

syntaxes/css.tmLanguage.json

@@ -557,6 +557,9 @@
 							},
 							"name": "meta.at-rule.supports.body.css",
 							"patterns": [
+								{
+									"include": "#nesting-at-rules"
+								},
 								{
 									"include": "$self"
 								}