Bug: `MalformedLocatorException` thrown for `id`s that don't start with a character (HTML 5)

These both result in an `MalformedLocatorException`:
```php
$I->seeElement(['id' =>'123']);
$I->seeElement(['css' =>'div#123']);
```
The reason is probably that up to HTML 4, `id`s were required to start with a character (a-z). However, in HTML 5, `id`s can begin with virtually anything: https://html.spec.whatwg.org/multipage/dom.html#the-id-attribute

首先，在 WebDriver 模块中复现 issue 里的两个 PHP seeElement 示例，并检查它们所涉及的 locator 处理。根据 HTML 5 规则，当以数字开头的 ID 无论通过 ID selector 还是 CSS selector 都不再引发 MalformedLocatorException 时，修复即完成。

由索引模型根据 Issue 内容生成。