Migrate English chapter visualisations to new format

[tunetheweb]

Follow on from #491 for the rest of the chapters.

Fixes #432
Fixes #428
Makes progress on #413 (comment)
Makes progress on #379

[tunetheweb]

As discussed in #491 (comment) I think we're good to submit this for other chapters once you are.

[rviscomi]

Need to resolve a few merge conflicts. Let me know if this is ok to review after that.

[tunetheweb]

Need to resolve a few merge conflicts. Let me know if this is ok to review after that.

Done!

[tunetheweb]

@rviscomi since we turned the JavaScript chapter on last night as a third chapter on the new format, we've already seen a bigger increase in GA data, which is shown below:

A few things to note:

• Low enough visitors who have sheets-access blocked (0.26%). This will be lower at weekends as suspect it'll be corporates normally blocking, but even so it's very low. It appears my company is an outlier!
• Low enough visitors who have canvas issues (0.47%). I checked and these are all iPads btw and iPads are approximately 2% of our visitors according to GA.
• However what we do see, which is more interesting for this change, is that the majority do not enable the interactive figures - and this is because they are on mobile. The new logic therefore be a data saver and performance boast for these users since currently the sheets are being loaded even with display style set to none. I'd be interested in seeing if the new report in Google Search Console leveraging CrUX data show any difference but that'll probably take a few days/weeks to feed through I presume?

Anyway, haven't seen or heard about any issues so I think we're ready to go live with the rest of the chapters if you are comfortable with this and get a chance to review them in this PR?

[rviscomi]

Your GA analysis SGTM so let's ship it. I didn't go through each line in the PR, I trust everything works.

[tunetheweb]

Thanks! That's merged to master and production now. Going to spend a bit testing it all again in production branch to make sure nothing missed and then will push out shortly.