Remove end date check if not specified (better 32-bit support)

[Sogl]

Related to #898

I can't find better way to remove it with DRY principle 😑
With smaller code we need to check a value for each $this->items iteration.

Also it can be used with PHP_INT_MAX with previous version of this code.

[flaviocopes]

Want to try this solution? (moved the if inside the loop)

    public function dateRange($startDate, $endDate = false, $field = false)
    {
        $start = Utils::date2timestamp($startDate);
        $end = $endDate ? Utils::date2timestamp($endDate) : false;

        $date_range = [];

        foreach ($this->items as $path => $slug) {
            $page = $this->pages->get($path);
            $add = false;

            if ($page !== null) {
                $date = $field ? strtotime($page->value($field)) : $page->date();

                if ($end) {
                    if ($date >= $start && $date <= $end) {
                        $add = true;
                    }
                } else {
                    if ($date >= $start) {
                        $add = true;
                    }
                }

                if ($add) {
                    $date_range[$path] = $slug;
                }
            }
        }

        $this->items = $date_range;

        return $this;
    }

[Sogl]

It looks better, but brings 3 if conditions on each item iteration...

[flaviocopes]

Merged yours