fix: Using covariant interface for IParser and IParseResult.

Rename CanonSharp.Common to CanonSharp.Pascal.

CanonSharp.Tests/CombinatorsTests/LinqTests.cs

@@ -10,7 +10,7 @@ public class LinqTests : ParserTestsBase
     [Fact]
     public void SelectTest1()
     {
-        Parser<char, string> parser = from token in Char('a')
+        IParser<char, string> parser = from token in Char('a')
             select token.ToString();
         ValidateSuccessfulResult(parser, "a", "a");
         ValidateFailedResult(parser, "b");
@@ -19,7 +19,7 @@ public class LinqTests : ParserTestsBase
     [Fact]
     public void SelectManyTest1()
     {
-        Parser<char, int> parser = from _1 in Char('a')
+        IParser<char, int> parser = from _1 in Char('a')
             from _2 in Char('b')
             from _3 in Char('c')
             select 123;