Updates to 3rd party libraries

Add Dockerfile and specific docker-php.ini

inc/vendor/phpoffice/phpspreadsheet/tests/PhpSpreadsheetTests/Helper/HtmlTest.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Helper;
+
+use PhpOffice\PhpSpreadsheet\Helper\Html;
+use PHPUnit\Framework\TestCase;
+
+class HtmlTest extends TestCase
+{
+    /**
+     * @dataProvider providerUtf8EncodingSupport
+     *
+     * @param mixed $expected
+     * @param mixed $input
+     */
+    public function testUtf8EncodingSupport($expected, $input)
+    {
+        $html = new Html();
+        $actual = $html->toRichTextObject($input);
+
+        self::assertSame($expected, $actual->getPlainText());
+    }
+
+    public function providerUtf8EncodingSupport()
+    {
+        return [
+            ['foo', 'foo'],
+            ['können', 'können'],
+            ['русский', 'русский'],
+            ["foo\nbar", '<p>foo</p><p>bar</p>'],
+        ];
+    }
+}