feat: move Expectations API out of external plugin

tests/Features/Expect/toBeInfinite.php

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