Improvements

• [VTTParser] Support for lineAlign and positionAlign by @eduter in #4773
• [TextTracks] Improve performance of addCaptions and fix duplicate check by @eduter in #4776
• add check for schemeIdUri in getIsMain() by @stschr in #4779

Bugfixes

• fix: allow large ints to be passed in as time values for processUriTemplate by @littlespex in #4775
• Fix regression when setting size of VTT cue by @dsilhavy in #4780
• fix: Handle falsey values in DescriptorType value property by @stephanterning in #4784