feat(expect): add more methods

tests/Expect/toBeNAN.php

@@ -0,0 +1,16 @@
+<?php
+
+use PHPUnit\Framework\ExpectationFailedException;
+
+test('pass', function () {
+    expect(asin(2))->toBeNan();
+    expect(log(0))->not->toBeNan();
+});
+
+test('failures', function () {
+    expect(1)->toBeNan();
+})->throws(ExpectationFailedException::class);
+
+test('not failures', function () {
+    expect(acos(1.5))->not->toBeNan();
+})->throws(ExpectationFailedException::class);