Essential whitespace get trimmed #112
Description
See #1 (comment) for this issue.
Example
<tt xmlns="http://www.w3.org/ns/ttml" xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
xmlns:tts="http://www.w3.org/ns/ttml#styling"
xmlns:itts="http://www.w3.org/ns/ttml/profile/imsc1#styling" xml:lang="">
<head>
<layout>
<region xml:id="r2" tts:displayAlign="center" tts:writingMode="lrtb"
tts:extent="82% 20%" tts:showBackground="whenActive" tts:origin="10% 71%"
tts:backgroundColor="#00000072" tts:fontFamily="Verdana"/>
</layout>
</head>
<body>
<div tts:textAlign="center">
<p tts:color="#ffffffff" tts:fontSize="125%" region="r2" end="00:00:01.500">
<span>Wecome to Geneva</span><span tts:backgroundColor="green"> 2020!</span>
</p>
</div>
</body>
</tt>Current behaviour
