Added parameter feature

[alperklc]

Added parameter support to the component.

For now, we only have disablePastDays parameter. We will add needed parameters later.

Usage:

  var params = {
      disablePastDays: true
  };

  vanillaCalendar.init(params);

Also added a changelog file, in order to document changes to this project.

[chrissy-dev]

@alperklc Thanks for the PR, I'll have a look over it later on today.

[chrissy-dev]

@alperklc Merged. 👍