Validate against unknown RRULE properties.

[mtvbrianking]

Current behavior

If an invalid property is included in the RRULE string, it will be ignored on the creation of the RRULE object.

$rule = new \Recurr\Rule('FREQ=MONTHLY;BYDAY=-1FR;COUNT=10;SKIP=5');

The above works properly

Desired behavior

$rule = new \Recurr\Rule('FREQ=MONTHLY;BYDAY=-1FR;COUNT=10;SKIP=5');

Exception:

Recurr\Exception\InvalidRRule with message 'Unknown RRULE property: SKIP

Why?

If you rely on storing RRULE string in your database and recreating them in PHP and JS then the same rule will pass for PHP using this package but fail in JS.