LibWeb: Whitespace that causes a line to wrap should be hidden

We were only pruning trailing whitespace on lines. This patch makes it
so we also don't add whitespace as the leading line box fragment on new
lines.

This logic is pretty crufty and I think we can do better, but for now
I've just made it handle this extra case so we can stop having lines
that start with a space character. :^)

Libraries/LibWeb/Layout/LineBox.cpp

@@ -73,10 +73,10 @@ void LineBox::trim_trailing_whitespace()
     }
 }
 
-bool LineBox::ends_in_whitespace() const
+bool LineBox::is_empty_or_ends_in_whitespace() const
 {
     if (m_fragments.is_empty())
-        return false;
+        return true;
     return m_fragments.last().ends_in_whitespace();
 }