Deindent rendered list item contents

[gibson042]

Line breaks in list items contents are preserved in output, but the indenting white space following them should be stripped. This will improve the rendering sought by tc39/ecmarkup#513 .

Exaggerated effects
ecmarkdown input

1. Item 1
                      1. Item 2
                         Item 2 line 2

output HTML

 <ol><li>Item 1<ol><li>Item 2
-                         Item 2 line 2</li></ol></li></ol>
+Item 2 line 2</li></ol></li></ol>

rendered output

• Item 1
  • Item 2
    ·························25 removed spacesItem 2 line 2