IMPORTANT: Before using this code, please make sure you have backups of your precious Org files. Also, it is recommended to create a new, empty calendar on your server for using this package.
ALSO IMPORTANT: When using this package, possibly all Org entries will
get an UID property (see the docstring of org-icalendar-store-UID for
further details). If you don’t want this, then do not use this
package; there is just no way around that. It is the only reliable way
to uniquely identify Org entries.