Add new db.m8g instances (#787)

Co-authored-by: Greg Netsman <[email protected]>

Author: gnetsman

rules/aws_db_instance_invalid_type.go

@@ -122,6 +122,15 @@ func NewAwsDBInstanceInvalidTypeRule() *AwsDBInstanceInvalidTypeRule {
 			"db.m7g.2xlarge":            true,
 			"db.m7g.xlarge":             true,
 			"db.m7g.large":              true,
+			"db.m8g.large":              true,
+			"db.m8g.xlarge":             true,
+			"db.m8g.2xlarge":            true,
+			"db.m8g.4xlarge":            true,
+			"db.m8g.8xlarge":            true,
+			"db.m8g.12xlarge":           true,
+			"db.m8g.16xlarge":           true,
+			"db.m8g.24xlarge":           true,
+			"db.m8g.48xlarge":           true,
 			"db.mv11.24xlarge":          true,
 			"db.mv11.12xlarge":          true,
 			"db.mv11.4xlarge":           true,