feat(expect): add more methods

tests/Expect/toBeInt.php

@@ -0,0 +1,16 @@
+<?php
+
+use PHPUnit\Framework\ExpectationFailedException;
+
+test('pass', function () {
+    expect(42)->toBeInt();
+    expect(42.0)->not->toBeInt();
+});
+
+test('failures', function () {
+    expect(42.0)->toBeInt();
+})->throws(ExpectationFailedException::class);
+
+test('not failures', function () {
+    expect(6 * 7)->not->toBeInt();
+})->throws(ExpectationFailedException::class);