Add Backdrop usage count in our Showcase page

[klonos]

We should be grabbing the total count of sites using Backdrop and adding it dynamically in our Showcase page. Mockup:

...we could link the number to https://backdropcms.org/project/usage or https://backdropcms.org/project/usage/backdrop

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PR: #496

[klonos]

related: #481

[quinnanya]

I really like tying that number to that page -- I know you can get to that number elsewhere, but it's helpful to see it in the context of specific examples.

[jenlampton]

I love this!

[serundeputy]

PR: #496

Not sure if I got the CMI part correct; my local wouldn't work if I pointed my active directory to dev-active; so I pointed to live-active placed the block then copied the changes to dev-active and committed that. 🤷‍♀️

[jenlampton]

You can always import a fresh db, and then manually copy everything from live-active to dev-active and commit it all.

[klonos]

(not tested the actual thing - from the screenshot): It seems that we have too many titles and too much text in the header section of that page (and I also do not like the words "use" and "using" here). We could shorten the whole thing to something like:

730 websites currently built with Backdrop CMS
Here are a few examples. Add your own!

[jenlampton]

What about:
Number of websites running on Backdrop CMS: 730
Here are a few examples. Add your own!

[ghost]

Here's a new PR inspired by @serundeputy's: #712

And here's what it looks like:

Rather than displaying the exact number (which looked odd in a title), I rounded down to the nearest hundred. And I aslo added a '+' after the number since that's only the number of sites that report back, there are likely more we don't know about.

[ghost]

I wonder if we should put a link to the source of that number (i.e./project/usage/backdrop) in there somewhere...? Something like: