Support comments in JSON

JSON spec doesn't allow comments, but many implementation support them anyway. Having comments is very convenient, for example, when showing code in blog posts and articles.

lexers/j/json.go

@@ -23,6 +23,9 @@ func jsonRules() Rules {
 		"whitespace": {
 			{`\s+`, Text, nil},
 		},
+		"comment": {
+			{`//.*?\n`, CommentSingle, nil},
+		},
 		"simplevalue": {
 			{`(true|false|null)\b`, KeywordConstant, nil},
 			{`-?(0|[1-9]\d*)(\.\d+[eE](\+|-)?\d+|[eE](\+|-)?\d+|\.\d+)`, LiteralNumberFloat, nil},
@@ -37,18 +40,21 @@ func jsonRules() Rules {
 		},
 		"objectvalue": {
 			Include("whitespace"),
+			Include("comment"),
 			{`"(\\\\|\\"|[^"])*"`, NameTag, Push("objectattribute")},
 			{`\}`, Punctuation, Pop(1)},
 		},
 		"arrayvalue": {
 			Include("whitespace"),
 			Include("value"),
+			Include("comment"),
 			{`,`, Punctuation, nil},
 			{`\]`, Punctuation, Pop(1)},
 		},
 		"value": {
 			Include("whitespace"),
 			Include("simplevalue"),
+			Include("comment"),
 			{`\{`, Punctuation, Push("objectvalue")},
 			{`\[`, Punctuation, Push("arrayvalue")},
 		},