`page.rs.html` used to result in a function `templates::page`.
Since ructe 0.7.2, `templates::page_html` was used and now the old alias
has been removed.
This changed the cache structure to allow caching data for multiple
branches. The service still assumes a default branch named `master` but
using the `branch` get parameter, the default branch can be changed.
The 404 page for the missing `master` branch was changed to explain the
new parameter.