[Task]: Include canonical <link> for user review pages

[diox]

Description

Currently, our add-on user review pages:

• Supports a ?score query parameter to filter the contents
• Don't have a <link rel=canonical>
• Have a <meta name="robots" content="noindex, follow" /> only when a ?review is passed
• Don't have <link rel=alternate> for other languages

We should:

• Add a <link rel=canonical> (ignore querystring: the "first" page with no querystring should be the canonical for now)
• Add <link rel=alternate> for main languages like we do on other pages
• Add a <meta name="robots" content="noindex, follow" /> when score is passed
• Add a rel=nofollow to links on the add-on detail page filtering user reviews by score

Just adding this in src/amo/pages/AddonReviewList/index.js should probably take care of the first 2 items:

{addon && !reviewId && (
  <HeadLinks />
)}

Acceptance Criteria

### Acceptance Criteria
- [ ] `<link rel=canonical>` is set correctly in user review pages
- [ ] `<link rel=alternate>` is set correctly in user review pages
- [ ] `rel=nofollow` is set on links on the add-on detail page filtering user reviews by score

Checks

• [X] If the issue is ready to work on, I have removed the "needs:info" label.

┆Issue is synchronized with this Jira Task

[diox]

Add a <meta name="robots" content="noindex, follow" /> when score is passed

We actually don't need to do that if a <link rel=canonical> is set correctly (pointing to the page without any query string). If search engines do stumble upon the URL with the score being passed and the canonical link on that page points them to the URL without any query string, we should be OK.

[ioanarusiczki]

I checked with https://addons-dev.allizom.org/fr/firefox/addon/ghosttext/reviews/, found:

rel="canonical" with href="https://addons-dev.allizom.org/fr/firefox/addon/ghosttext/reviews/" even when ?score is passed rel="nofollow" for the links from the add-on detail page which filter reviews by score

I don't see <link rel=alternate> for languages, I'm looking into html's head on reviews page.

[diox]

It see them:

(...)
<link data-react-helmet="true" href="https://addons-dev.allizom.org/en-US/firefox/addon/ghosttext/reviews/" hrefLang="x-default" rel="alternate"/>
<link data-react-helmet="true" href="https://addons-dev.allizom.org/en-US/firefox/addon/ghosttext/reviews/" hrefLang="en" rel="alternate"/>
<link data-react-helmet="true" href="https://addons-dev.allizom.org/pt-PT/firefox/addon/ghosttext/reviews/" hrefLang="pt" rel="alternate"/>
(...)

[ioanarusiczki]

I had https://addons-dev.allizom.org/en-US/firefox/addon/ghosttext/reviews/?utm_content=homepage-primary-hero&utm_medium=referral&utm_source=addons.mozilla.org because I navigated to the detail page from the primary hero suggestion, in this case I only saw the canonical link.

Once I removed ?utm_content=homepage-primary-hero&utm_medium=referral&utm_source=addons.mozilla.org they show up.

[diox]

Yeah, that's expected.