Represents a textual component of an HTML-like label. It is assumed
that a
Label list is non-empty. It is preferable to "group"
Str values together rather than have individual ones. Note that
when printing, the individual values are concatenated together without
spaces, and when parsing anything that isn't a tag is assumed to be a
Str: that is, something like "
<BR/> <BR/>"
is parsed as:
[Newline [], Str " ", Newline []]