Event : add export to more calendars

[agilare]

In Agenda and Event page, in addition to the current link to the ical format, for ex. https://ladecadanse.darksite.ch/evenement_ics.php?idE=382671

add links to export to common calendar tools like :

• Google Calendar - example https://calendar.google.com/calendar/render?action=TEMPLATE&dates=20230411T190000Z%2F20230411T210000Z&details=Le%20premier%20film%20pakistanais%20prim%C3%A9%20%C3%A0%20Cannes%20%3A%20Joyland%20de%20Saim%20Sadiq%20est%20au%20Cin%C3%A9lux%20%21%20Un%20kal%C3%A9idoscope%20d%27%C3%A9motions%20et%20de%20sensations%2C%20tr%C3%A8s%20bien%20nuanc%C3%A9%20par%20un%20sc%C3%A9nario%20digne%20des%20grands%20noms%20du%20cin%C3%A9ma%20%21%0A&location=%20Cin%C3%A9lux%09%20%20%20%20%20%208%2C%20bd%20Saint-Georges%20-%20Gen%C3%A8ve&text=JOYLAND%20de%20Saim%20Sadiq
• Outlook
• Office 365

Implementation example : https://www.cssscript.com/demo/add-events-calendars/

Useful links :

• form to create Add to Calendar links
• Official documentation

Conception

Adapt evenement_ics.php to generate more than 1 format, like evenement_export.php?format=ical|google...
For Google Calendar :

1. adapt event values for Google format
2. build url with these values
3. redir user to this url (instead of download like for ics)

Layout suggestion in agenda with 2 kind of exports available :

[agilare]

spatie/calendar-links 1.8.0 library could be used