feat(expressions): add date expression function

tests/src/flextype/core/Entries/Expressions/DateExpressionTest.php

@@ -0,0 +1,19 @@
+<?php
+
+use Flextype\Component\Filesystem\Filesystem;
+use function Glowy\Filesystem\filesystem;
+use function Flextype\entries;
+
+beforeEach(function() {
+    filesystem()->directory(FLEXTYPE_PATH_PROJECT . '/entries')->create();
+});
+
+afterEach(function (): void {
+    filesystem()->directory(FLEXTYPE_PATH_PROJECT . '/entries')->delete();
+});
+
+test('date expression', function () {
+    $date = date("F j, Y, g:i a");
+    entries()->create('date', ['test' => '[[ date("F j, Y, g:i a") ]]']);
+    expect(entries()->fetch('date')['test'])->toBe($date);
+});