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After 3 seconds, the plugin will finish initializing and mark the Calendar-border red. The returned promise is used to pop-up an alert.
This example uses a plugin that takes some time to do its job. We plug it in immediately, but want a promise that informs us when
the plugin is ready. The moment where the plugin is defined as 'ready', should be defined with the function promiseBeforeReady,
which should be redeclared by the developer.