Getting _ to sort to the top like it should (#1328)

closes #1327

Author: belav

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/UsingDirectives_UnderscoreSort.expected.test

@@ -0,0 +1,3 @@
+using SomeCompany._Word;
+using SomeCompany.MWord;
+using SomeCompany.ZWord;

Src/CSharpier.Tests/FormattingTests/TestFiles/cs/UsingDirectives_UnderscoreSort.test

@@ -0,0 +1,3 @@
+using SomeCompany.MWord;
+using SomeCompany.ZWord;
+using SomeCompany._Word;

Src/CSharpier/SyntaxPrinter/UsingDirectives.cs

@@ -292,14 +292,14 @@ public int Compare(UsingDirectiveSyntax? x, UsingDirectiveSyntax? y)
                 return string.Compare(
                     x.Alias.ToFullString(),
                     y.Alias.ToFullString(),
-                    StringComparison.OrdinalIgnoreCase
+                    StringComparison.InvariantCultureIgnoreCase
                 );
             }
 
             return string.Compare(
                 x?.Name?.ToFullString(),
                 y?.Name?.ToFullString(),
-                StringComparison.OrdinalIgnoreCase
+                StringComparison.InvariantCultureIgnoreCase
             );
         }
     }