Add #arithmetic-operators for function syntax

Author: jacobcassidy

syntaxes/css.tmLanguage.json

@@ -31,6 +31,10 @@
 		}
 	],
 	"repository": {
+    "arithmetic-operators": {
+      "match": "[*/]|(?<=\\s|^)[-+](?=\\s|$)",
+      "name": "keyword.operator.arithmetic.css"
+    },
 		"at-rules": {
 			"patterns": [
 				{
@@ -846,10 +850,9 @@
 					},
 					"name": "meta.function.calc.css",
 					"patterns": [
-						{
-							"match": "[*/]|(?<=\\s|^)[-+](?=\\s|$)",
-							"name": "keyword.operator.arithmetic.css"
-						},
+            {
+              "include": "#arithmetic-operators"
+            },
 						{
 							"include": "#property-values"
 						},
@@ -975,6 +978,9 @@
 							"match": "(?i)(?<=[,\\s\"]|\\*/|^)\\d+x(?=[\\s,\"')]|/\\*|$)",
 							"name": "constant.numeric.other.density.css"
 						},
+            {
+              "include": "#arithmetic-operators"
+            },
 						{
 							"include": "#property-values"
 						},
@@ -1108,10 +1114,9 @@
 						}
 					},
 					"patterns": [
-						{
-							"match": "[*/]|(?<=\\s|^)[-+](?=\\s|$)",
-							"name": "keyword.operator.arithmetic.css"
-						},
+            {
+              "include": "#arithmetic-operators"
+            },
 						{
 							"include": "#property-values"
 						},