Displaying the total number of files created during the last month

Using the implicit field file.cday works in local tests.

In the last month you have added `$= dv.pages('"Library" and #Book').filter(page => new Date(page.file.cday).getMonth() === 3).length` books in this library.

:thinking:

https://blacksmithgu.github.io/obsidian-dataview/annotation/types-of-metadata/#date