Add comments to clarify hyphenation logic and structure in Epub processing

lib/Epub/Epub/hyphenation/Hyphenator.h

@@ -6,6 +6,7 @@
 
 class GfxRenderer;
 
+// Holds the split portions of a hyphenated word.
 struct HyphenationResult {
   std::string head;
   std::string tail;
@@ -13,6 +14,7 @@ struct HyphenationResult {
 
 class Hyphenator {
  public:
+  // Splits a word so it fits within availableWidth, appending a hyphen to the head when needed.
   static bool splitWord(const GfxRenderer& renderer, int fontId, const std::string& word, EpdFontStyle style,
                         int availableWidth, HyphenationResult* result, bool force);
 };