add leading and trailing whitespace to text nodes

[milahu]

fix #87

[amaanq]

should the first newline even be considered? what about text: _ => /[^<>&\n][^<>&]*/?

[milahu]

yes, the parser should be lossless
everything outside of tags should be parsed as text

the text regex could be even more greedy like /[^<&]+/ to allow > in text
but i cant remember if i tested that
maybe > is already parsed as "unescaped entity >" which would be a bit wasteful