Add character specific class to each char

[bartveneman]

For kerning purposes it would be nice to be able to target specific characters. Proposed output:

<h1>
  <span class="char1 char-a">A</span>
  <span class="char2 char-l">l</span>
  <span class="char3 char-p">p</span>
  <span class="char4 char-h">h</span>
  <span class="char5 char-a">a</span>
</h1>

Should investigate what this could do for special characters like é and &. Perhaps it would be nice to output the html entity name? Anyway, maybe map special entities to charcodes, or something like that.

<span class="char1 char-amp">&amp;</span>
<span class="char2 char-code38">&</span>