Pre-open section linked to in anchor

Adds `GOVUK.getCurrentLocation()` which returns `window.location` so
that we can stub the return value in tests.
Fix line width for headerless sections

When starting a document with something other than a <h2>, the body of
the section was being incorrectly displayed as full width. This commit
wraps everything in the body up until the first <h2> in a div allowing
us to style it.
Merge pull request #64 from alphagov/open-section-linked-to-with-anchor

Pre-open section linked to in anchor
Merge pull request #65 from alphagov/fix-line-wrapping

Fix line width for sections without <h2>
Link to the API representation

I found myself wanting this to get at the Content API format.

Additionally, the Service Manual suggests that we do it:
https://www.gov.uk/service-manual/making-software/apis.html#representations-are-for-the-consumer
Merge pull request #66 from alphagov/link_to_api_representation

Link to the API representation
Bump slimmer to 4.2

In 4.1.1 we've swapped from loading test assets from preview to loading
them from production. That should quieten down most of the intermittent
test failures we're getting due to timeouts.
Merge pull request #67 from alphagov/bump-slimmer

Bump slimmer to 4.2
Bump gds-api-adapters to 14.1.0

This picks up the Content Store adapter.
Limit width of Manual and Document summaries

This commit limits the width of Manual and Document summaries in order
to bring it in line with the rest of the body content in Documents.

This also fixes an issue with the bug fix for line width on content in
the body. It does this by using the CSS not selector to go through all
children except h2s, so it will never skip the first element in
.govspeak, which might be a h2.
Merge pull request #68 from alphagov/limit-width-of-summary

Limit width of Manual and Document summaries
Merge pull request #69 from alphagov/bump-gds-api-adapters

Bump gds-api-adapters to 14.1.0
Fix for collapsible sections width issue

With the fix introduced in #68, there was an issue were it was finding
the first element which wasn't a h2, when it should have been starting
at the first element and doing nothing if it was a h2. This commit fixes
that bug.

Also testing the headerlessContent function.
Merge pull request #70 from alphagov/fix-for-collapsible-manuals-width-issue

Fix for collapsible sections width issue