Checks for missing constant typehints (#26)

[Docs](https://github.com/slevomat/coding-standard/blob/master/doc/type-hints.md#slevomatcodingstandardtypehintsclassconstanttypehint-)

Author: spaze

composer.json

@@ -14,7 +14,7 @@
 	],
 	"require": {
 		"php": "^7.2 || ^8.0",
-		"slevomat/coding-standard": "^8.11"
+		"slevomat/coding-standard": "^8.16"
 	},
 	"require-dev": {
 		"ext-simplexml": "*"

src/ruleset.xml

@@ -130,6 +130,7 @@
 		</properties>
 	</rule>
 	<rule ref="SlevomatCodingStandard.PHP.UselessSemicolon"/>
+	<rule ref="SlevomatCodingStandard.TypeHints.ClassConstantTypeHint"/>
 	<rule ref="SlevomatCodingStandard.TypeHints.DeclareStrictTypes">
 		<properties>
 			<property name="linesCountBeforeDeclare" value="0"/>