mdn: adapt for yari

[myfreeer]

Recently, mdn has switched its backend to yari, which has changed a lot of its behavior.

Below is an incomplete list of changes:

• Pages not available in current locale but available in english would result in 404 (mdn: manually fallback 404 to en-US pages #196)
• Browser compatibility table is rendered in browser side, via ajax, instead of server-side. (mdn: manually rendering the compatibility table #194)
• Some links are replaced with ajax and in-place render, but following the link would still work. (commit 4720480)
• Sitemaps are likely to be gzipped. (mdn: parse gzip compressed sitemap #214)
• Scripts are packed with webpack and is likely to have runtime-loaded script chunks. (Sign-in modal) (commit 4720480)
• Links in header bar is nolonger localized.
• Many redirects are missing and many archived contents were gone. (Even if they are in search results)
• Many translated redirects are missing, but the content is still there with the sitemap as the only entrance. (translation_of and translation_of_original not parsed)
• Style of old compatibility table is gone. (commit 8f45406)

To adapt for that, we might need to:

• Manually fallback to en-US in case of 404. (mdn: manually fallback 404 to en-US pages #196)
• Drop all the scripts or mock fetch api with a more complete response list, or drop all the scripts and manually implement the ui actions with js or css. (mdn: reimplementing mdn ui #193) (mdn: adapt for the new ui again #534)
• Get the browser compatibility table and render it to page manually or mock the api. (mdn: manually rendering the compatibility table #194) (mdn: update the compatibility table #629) (update the ui scripts of the compatibility table #630)
• Prevent attaching events to links or stopImmediatePropagation before SPA rendering invoked.
• Inject back the style of old compatibility table (commit 8f45406)

[myfreeer]

Browser compatibility table seems complex for rendering.
Link: #194

[myfreeer]

Main page is not localized now