2.0.0

• Bump required PHP version to ^8.0
• Fix bug with overlapAll when no overlap
• All period properties are now typed, this affects you if you extend from Period or PeriodCollection
• Return types of several methods have been changed from Period to static
• Period::duration() returns an instance of PeriodDuration
• Period::length() now uses the Period's precision instead of always returning days
• Period::overlap() renamed to Period::overlapAny()
• Period::overlapSingle() renamed to Period::overlap()
• Period::diff() renamed to Period::subtract()
• Period::subtract() (previously diff) no longer returns the gap when there's no overlap
• Period::diffSingle() renamed to Period::diffSymmetric()
• Period::contains() now accepts both DateTimeInterface and Period
• PeriodCollection::overlap() now accepts one or several periods
• Renamed all getters like getIncludedEnd() and getStart() to includedEnd() and start(), etc.
• Add Period::fromString()
• Add Period::asString()