Only indent paragraphs for justify/left-align (#367)

Currently, when Extra Paragraph Spacing is off, an em-space is added to
the beginning of each ParsedText even for blocks like headers that are
centered. This whitespace makes the centering slightly off. Change the
calculation here to only add the em-space for left/justified text.

Co-authored-by: Maeve Andrews <maeve@git.mail.maeveandrews.com>

lib/Epub/Epub/ParsedText.cpp

@@ -43,7 +43,7 @@ std::vector<uint16_t> ParsedText::calculateWordWidths(const GfxRenderer& rendere
   wordWidths.reserve(totalWordCount);
 
   // add em-space at the beginning of first word in paragraph to indent
-  if (!extraParagraphSpacing) {
+  if ((style == TextBlock::JUSTIFIED || style == TextBlock::LEFT_ALIGN) && !extraParagraphSpacing) {
     std::string& first_word = words.front();
     first_word.insert(0, "\xe2\x80\x83");
   }