Add a grid layout to the choose services page

This allows us to split the page into sections without over-using bold
fonts. And it means that when the user clicks into a service from this
page the column layout stays the same 1/4 – 3/4, rather than jumping
about so much.

tests/app/main/views/organisations/test_organisation.py

@@ -37,7 +37,7 @@ def test_organisation_page_shows_all_organisations(
 
     assert normalize_spaces(
         page.select_one('h1').text
-    ) == "Organisations"
+    ) == "All organisations"
 
     for index, org in enumerate(orgs):
         assert page.select('a.browse-list-link')[index].text == org['name']