[Website] Add Google Analytics tags to C++, Python API docs

[asfimport]

It would be helpful to see which parts of the documentation are seeing traffic

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

PRs and other links:

• GitHub Pull Request #2666

_{Note: This issue was originally created as ARROW-3076. Please see the migration documentation for further details.}

[asfimport]

Uwe Korn / @xhochy:
We should also add the relevant GDPR-related consent notices then.

[asfimport]

Wes McKinney / @wesm:
Here is the JS site tag

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-107500873-1"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());

  gtag('config', 'UA-107500873-1');
</script>

I don't know what needs to be done for the GDPR requirement, can you advise?

[asfimport]

Uwe Korn / @xhochy:
No, we probably have to read a bit on that. The solution to my private blog was to remove any external trackers.

[asfimport]

Wes McKinney / @wesm:
Ok. I found https://www.blastam.com/blog/5-actionable-steps-gdpr-compliance-google-analytics. We don't collect any PII in our URLs and users do not log into the website at all, so it may just involve turning on IP anonymization

[asfimport]

Kouhei Sutou / @kou:
Issue resolved by pull request 2666
#2666