feat: Extract author from XTC/XTCH files (#563)

## Summary

* Extract author from XTC/XTCH files

## Additional Context

* Based on updated details in
https://gist.github.com/CrazyCoder/b125f26d6987c0620058249f59f1327d

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? No

lib/Xtc/Xtc/XtcParser.h

@@ -67,8 +67,9 @@ class XtcParser {
                              std::function<void(const uint8_t* data, size_t size, size_t offset)> callback,
                              size_t chunkSize = 1024);
 
-  // Get title from metadata
+  // Get title/author from metadata
   std::string getTitle() const { return m_title; }
+  std::string getAuthor() const { return m_author; }
 
   bool hasChapters() const { return m_hasChapters; }
   const std::vector<ChapterInfo>& getChapters() const { return m_chapters; }
@@ -86,6 +87,7 @@ class XtcParser {
   std::vector<PageInfo> m_pageTable;
   std::vector<ChapterInfo> m_chapters;
   std::string m_title;
+  std::string m_author;
   uint16_t m_defaultWidth;
   uint16_t m_defaultHeight;
   uint8_t m_bitDepth;  // 1 = XTC/XTG (1-bit), 2 = XTCH/XTH (2-bit)
@@ -96,6 +98,7 @@ class XtcParser {
   XtcError readHeader();
   XtcError readPageTable();
   XtcError readTitle();
+  XtcError readAuthor();
   XtcError readChapters();
 };