Force long table cell text to break

The resulting line-broken text isn't necessarily pretty, but this does
solve the problem on the API Users page where long email addresses can
result in the <table> being wider than its container
(div.govuk-width-container).

I'm not sure how widely useful this is and therefore how to handle this
when we're ready to merge our other changes back into the components
gem.

app/assets/stylesheets/components/_table.scss

@@ -127,3 +127,9 @@ $table-row-even-background-colour: govuk-colour("light-grey", $legacy: "grey-4")
   }
 }
 /* stylelint-enable */
+
+.app-c-table {
+  tbody tr td {
+    word-break: break-word;
+  }
+}