Added initial version 0.1.0

Runtime/Attributes/RequiredAttribute.cs

@@ -0,0 +1,29 @@
+using System;
+
+namespace Module.ProjectValidator
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = true)]
+    public sealed class RequiredAttribute : Attribute
+    {
+        private readonly EValidatorSeverity _severity;
+
+        public RequiredAttribute()
+        {
+            _severity = EValidatorSeverity.Error;
+        }
+        
+        public RequiredAttribute(EValidatorSeverity severity)
+        {
+            _severity = severity;
+        }
+        
+        public sealed class Validator : IAttributeValidator<RequiredAttribute>
+        {
+            public ValidatorResult Validate(RequiredAttribute attribute, object value)
+            {
+                var isValid = value is UnityEngine.Object obj ? obj != null : value != null;
+                return isValid ? ValidatorResult.Valid : ValidatorResult.Create(attribute._severity, "Value is Null");
+            }
+        }
+    }
+}