Add Type::toBitwiseNotType() to AccessoryDecimalIntegerStringType

This class was added on the `unsealed` branch and didn't exist when
the `Type::toBitwiseNotType()` interface method was introduced in
the merged Group 3 refactor — sync up the missing override so the
class is instantiable again.

Body matches the other accessory string types: when not inverted the
type is guaranteed non-empty, so `~$s` keeps the non-empty
accessory. The decimal-integer property itself doesn't survive
bitwise-not, so the accessory is dropped.

Author: ondrejmirtes

src/Type/Accessory/AccessoryDecimalIntegerStringType.php

@@ -220,6 +220,18 @@ public function toAbsoluteNumber(): Type
 		return $this->toNumber()->toAbsoluteNumber();
 	}
 
+	public function toBitwiseNotType(): Type
+	{
+		// Decimal integer strings are non-empty when not inverted
+		// (`"0"` / `"123"` are still at least one character). `~$s`
+		// returns a string of the same length, so the non-empty flag
+		// survives. The decimal-integer property doesn't survive the
+		// bitwise-not, hence we drop the accessory.
+		return $this->isNonEmptyString()->yes()
+			? new IntersectionType([new StringType(), new AccessoryNonEmptyStringType()])
+			: new StringType();
+	}
+
 	public function toBoolean(): BooleanType
 	{
 		return $this->isNonFalsyString()->negate()->toBooleanType();