[DOC] - Add Developmental Demo to the docsite examples page

[TomDonoghue]

This adapts the Developmental Data example, from here into an example to be hosted on the documentation website.

In terms of content, it's about the same, just edited in format for hosting, and with some mild updates to match current version 1.1.

For ease of checking / reviewing - here is a copy of the built documentation including what's added:
html.zip
^If you download and unzip this, it's a copy of the built documentation page. Open the html folder, and double click 'index.html' to open the home page in a browser. Then you can click on the examples tab, and under the analyses section, click and see the new "Developmental Data Demo" example.

[TomDonoghue]

Adding a note here that I checked this with Brendan, from the DevDemo project, and sounds like it looks good - so merging in!