Add support for pre-55 calendar

Background: There are many discrepancies between the Divino Afflatu "pre-55" calendar and the 1962 calendar. For example, in the "pre-55" calendar, April 22, 2026, is the Patronage of St. Joseph, Confessor (being Wednesday before the third Sunday after Easter), while in the 1962 calendar, it's Sts. Soter and Caius, Popes and Martyrs.

Context: The Lasance Missal of 1945 obviously reflects the pre-55 calendar and rubrics, and the church that I frequent follows the pre-55 calendar in most cases.

Feature Request: When I select the Lasance missal, then I should be presented with the pre-55 calendar as the default, or at least be presented with the option to follow the pre-55 calendar.

Discussion: It looks like Missal Page is already using parts of DivinumOfficium.org for Mass propers. Divinum Officium offers a plethora of liturgical calendar options, including the 1945 Divino Afflatu version.