fix passing WebElement-type arguments to ExecuteScript
fix passing WebElement-type arguments to ExecuteScript

Make it such that `WebElement` interfaces originating from this package can be
passed as arguments to `WebDriver.ExecuteScript` per section "10. Elements",
paragraph "When asked to serialize the element element" of the W3C WebDriver
specification (https://www.w3.org/TR/webdriver).

sourcegraph/go-selenium