Define additional request parameters for navigate

See whatwg/fetch#126 for context around the
“navigate” value for request’s mode. The other additions were
unfortunately omitted from 7c5555a.

source

@@ -82012,7 +82012,11 @@ State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON O
        <span>source browsing context</span>'s <span>active document</span>'s <code>Window</code>
        object's <span>environment settings object</span>, <span
        data-x="concept-request-target-browsing-context">target browsing context</span> to the
-       <span>browsing context</span> being navigated, and <span
+       <span>browsing context</span> being navigated, <span
+       data-x="concept-request-destination">destination</span> to "<code data-x="">document</code>",
+       <span data-x="concept-request-mode">mode</span> to "<code data-x="">navigate</code>", <span
+       data-x="concept-request-credentials-mode">credentials mode</span> to "<code
+       data-x="">include</code>", <span>use-URL-credentials flag</span>, and <span
        data-x="concept-request-redirect-mode">redirect mode</span> to "<code
        data-x="">manual</code>".</p></li>