Use a base template to create a cohesive feel across the HTML
templates provided by Synapse.
Adds basic styling to the base template for a more user-friendly
look and feel.
When registering a new account via SSO on iOS, the text field becomes pretty annoying as it autocapitalises and autocorrects your input. This PR fixes that (although I have only tested the raw HTML file on the simulator, I'm not sure how to get the complete setup available for testing in the flow).
There's some prelimiary work here to pull out the construction of a jinja environment to a separate function.
I wanted to load the template at display time rather than load time, so that it's easy to update on the fly. Honestly, I think we should do this with all our templates: the risk of ending up with malformed templates is far outweighed by the improved turnaround time for an admin trying to update them.
