Added Philippine mobile number validation

Author: isaiahnoelsalazar

Check.cs

@@ -1,4 +1,5 @@
 using System.Collections;
+using System.Text.RegularExpressions;
 
 namespace CSSimpleFunctions
 {
@@ -66,6 +67,12 @@ public static bool IsValid(string str)
             }
         }
 
+        public static bool IsAValidPhilippineMobileNumber(string str)
+        {
+            string pattern = @"^(?:09|\+639|639)\d{9}$";
+            return Regex.IsMatch(Regex.Replace(str, @"[\s\-\(\)]", ""), pattern);
+        }
+
         public static bool HasNumbers(string str)
         {
             string numbers = "0123456789";

README.md

@@ -38,6 +38,13 @@ Check.HasSymbols("Sample text!"); // returns true
 Check.HasSpaces("Sample_text"); // returns false
 Check.HasSpaces("Sample text"); // returns true
 ```
+### IsAValidPhilippineMobileNumber
+- will check a String if it is a valid Philippine mobile number
+- returns a boolean value
+```csharp
+Check.IsAValidPhilippineMobileNumber("+15551234567"); // returns false
+Check.IsAValidPhilippineMobileNumber("09171234567"); // returns true
+```
 ### Email.AddValidDomainName
 - adds a valid domain name to the list of valid domain names
 ```csharp