feat(utils, templates, docs): file-based templates + stronger README

templates/problem/test/SolutionTests.cs.tmpl

@@ -0,0 +1,24 @@
+// LeetCode {{NUMBER}} 單元測試（xUnit）
+
+using Xunit;
+
+public class SolutionTests {
+    private readonly Solution _s = new Solution();
+
+    [Fact]
+    public void Example1() {
+        // TODO: Arrange
+        // var input = new int[] { };
+        // var expected = 0;
+        // Act
+        // var got = _s.Solve(input);
+        // Assert.Equal(expected, got);
+        Assert.True(true);
+    }
+
+    [Fact]
+    public void EdgeCases() {
+        Assert.True(true);
+    }
+}
+