Update default page template examples so default shows a heading inside a grid column

[edwardhorsford]

The default page template example does not include a grid row or column, and just has a heading inside of main.

I don't think services should ever do this. Pretty much all content should be within a 2/3 column - or at least one of the other grid columns. They should never have a heading inside main like that.

My suggestion would be to:

• Update the default page template example to include a grid row and 2/3 column, with size l heading inside of it.
• Update the customised page template example to include a more complex grid column arrangement.

Note the NHS example is pretty similar to the GOV.UK example. I've suggested on cross gov slack that it would be good for the default to change there too.