Add Blacklist Support

[CodebyCR]

Add blacklist support for removing specific dates like holidays and so on.

[CodebyCR]

This feature should shrink the default ranges.

Example:

// ...

const auto weekend = BlackList{.weekday="SAT,SUN"};

scheduler.blackList(weekend);

// The Watch don't execute something at Saturday or Sunday

// Compact Warning for execution times in this range