Feature request: Add an option to create recurring events on the last day of month

[microsoftsucksass]

There's an option to create an event on day 29/30/31 or last Monday-Sunday but no option to create such event on the last day of every month, which is odd.

[econdepe]

For the moment we're only supporting the most commonly used recurrence rules. One of the reasons for that is to maximize compatibility with other calendar providers (in case of sending invites or exporting the calendar). However we will look in the future to expand our supported set of recurrence rules, especially if it's demanded by the user community :)