Show the iCal sharing link instead of directly open it (references #141)

public/js/grocy.js

@@ -506,3 +506,8 @@ $(".locale-number-format[data-format='currency']").each(function ()
 {
 	$(this).text(parseFloat($(this).text()).toLocaleString(undefined, { style: "currency", currency: Grocy.Currency }));
 });
+
+$(document).on("click", ".easy-link-copy-textbox", function()
+{
+	$(this).select();
+});

public/viewjs/calendar.js

@@ -17,7 +17,10 @@ $("#ical-button").on("click", function(e)
 	Grocy.Api.Get('calendar/ical/sharing-link',
 		function(result)
 		{
-			location.href = result.url;
+			bootbox.alert({
+				title: L('Share/Integrate calendar (iCal)'),
+				message: L('Use the following (public) URL to share or integrate the calendar in iCal format') + '<input type="text" class="form-control form-control-sm mt-2 easy-link-copy-textbox" value="' + result.url + '">'
+			});
 		},
 		function(xhr)
 		{