Allow API calls to be made without .php in the path

[carrythebanner]

For backwards compatibility while transitioning the backend from PHP to Node, we intentionally maintained .php in API paths even though they were no longer PHP files, e.g. https://localhost:4443/api/events.php?startdate=2019-06-01&enddate=2019-06-15

(See implementation in https://github.com/shift-org/shift-docs/blob/main/app/app.js#L52)

We should drop .php from the canonical URLs, e.g. https://localhost:4443/api/events?startdate=2019-06-01&enddate=2019-06-15

For backwards compatibility we should proxy/redirect the .php paths to the new canonical path, but encourage clients to update their API calls to the new path.