Added missing severity levels

Author: jschick04

src/EventLogExpert.Eventing.Tests/EventResolvers/EventResolverBaseTests.cs

@@ -1612,10 +1612,11 @@ public void ResolveEvent_WithSeverityLevel_ShouldResolveLevelString()
         var testCases = new[]
         {
             (Level: (byte)0, Expected: "Information"),
+            (Level: (byte)1, Expected: "Critical"),
             (Level: (byte)2, Expected: "Error"),
             (Level: (byte)3, Expected: "Warning"),
             (Level: (byte)4, Expected: "Information"),
-            (Level: (byte)5, Expected: "5")
+            (Level: (byte)5, Expected: "Verbose")
         };
 
         foreach (var testCase in testCases)

src/EventLogExpert.Eventing/Helpers/SeverityMethods.cs

@@ -7,17 +7,21 @@ public enum SeverityLevel
 {
     Information,
     Warning,
-    Error
+    Error,
+    Critical,
+    Verbose
 }
 
 public static class Severity
 {
     public static string GetString(byte? level) => level switch
     {
         0 => nameof(SeverityLevel.Information),
+        1 => nameof(SeverityLevel.Critical),
         2 => nameof(SeverityLevel.Error),
         3 => nameof(SeverityLevel.Warning),
         4 => nameof(SeverityLevel.Information),
+        5 => nameof(SeverityLevel.Verbose),
         _ => level?.ToString() ?? string.Empty
     };
 }