Add only operator query operator

corpus/statements.txt

@@ -69,6 +69,7 @@ Media statements
 @media screen and (min-width: 30em) and (orientation: landscape) {}
 @media (min-height: 680px), screen and (orientation: portrait) {}
 @media not all and (monochrome) {}
+@media only screen {}
 
 ---
 
@@ -85,8 +86,9 @@ Media statements
     (binary_query (keyword_query) (feature_query (feature_name) (plain_value)))
     (block))
   (media_statement
-    (binary_query (negated_query (keyword_query)) (parenthesized_query (keyword_query)))
-    (block)))
+    (binary_query (unary_query (keyword_query)) (parenthesized_query (keyword_query)))
+    (block))
+  (media_statement (unary_query (keyword_query)) (block)))
 
 ==============================
 Supports statements
@@ -113,12 +115,12 @@ Supports statements
       (feature_query (feature_name) (plain_value)))
     (block))
   (supports_statement
-    (negated_query (parenthesized_query (binary_query
+    (unary_query (parenthesized_query (binary_query
       (feature_query (feature_name) (plain_value))
       (feature_query (feature_name) (plain_value)))))
     (block))
   (supports_statement
-    (negated_query (selector_query (pseudo_class_selector
+    (unary_query (selector_query (pseudo_class_selector
       (class_name)
       (arguments (tag_name) (tag_name)))))
     (block)))

grammar.js

@@ -214,7 +214,7 @@ module.exports = grammar({
       alias($.identifier, $.keyword_query),
       $.feature_query,
       $.binary_query,
-      $.negated_query,
+      $.unary_query,
       $.selector_query,
       $.parenthesized_query
     ),
@@ -239,8 +239,8 @@ module.exports = grammar({
       $._query
     )),
 
-    negated_query: $ => prec(1, seq(
-      'not',
+    unary_query: $ => prec(1, seq(
+      choice('not', 'only'),
       $._query
     )),
 

src/grammar.json

@@ -1031,7 +1031,7 @@
         },
         {
           "type": "SYMBOL",
-          "name": "negated_query"
+          "name": "unary_query"
         },
         {
           "type": "SYMBOL",
@@ -1120,15 +1120,24 @@
         ]
       }
     },
-    "negated_query": {
+    "unary_query": {
       "type": "PREC",
       "value": 1,
       "content": {
         "type": "SEQ",
         "members": [
           {
-            "type": "STRING",
-            "value": "not"
+            "type": "CHOICE",
+            "members": [
+              {
+                "type": "STRING",
+                "value": "not"
+              },
+              {
+                "type": "STRING",
+                "value": "only"
+              }
+            ]
           },
           {
             "type": "SYMBOL",