feat: Parser Combinator库和词法分析器 (#2)

Reviewed-on: https://git.bupt-hpc.cn/jackfiled/CanonSharp/pulls/2
Co-authored-by: jackfiled <xcrenchangjun@outlook.com>
Co-committed-by: jackfiled <xcrenchangjun@outlook.com>

CanonSharp.Tests/ReaderTests/StringReadStateTests.cs

@@ -0,0 +1,21 @@
+using CanonSharp.Combinator.Extensions;
+using CanonSharp.Common.Scanner;
+
+namespace CanonSharp.Tests.LexicalAnalyzerTests;
+
+public class StringReadStateTests
+{
+    [Fact]
+    public void AsEnumerableTest()
+    {
+        StringReadState state = new("abc");
+
+        IEnumerable<StringReadState> states = state.AsEnumerable<char, StringReadState>();
+
+        foreach ((char c, StringReadState s) in "abc".Zip(states))
+        {
+            Assert.True(s.HasValue);
+            Assert.Equal(c, s.Current);
+        }
+    }
+}