Custom zip parsing (#140)

## Summary

* Use custom zip central directory parsing to lower memory usage when
loading zipped epub content

lib/ZipFile/ZipFile.h

@@ -1,20 +1,46 @@
 #pragma once
-#include <Print.h>
+#include <FS.h>
 
 #include <string>
-
-#include "miniz.h"
+#include <unordered_map>
 
 class ZipFile {
-  std::string filePath;
-  mutable mz_zip_archive zipArchive = {};
-  bool loadFileStat(const char* filename, mz_zip_archive_file_stat* fileStat) const;
-  long getDataOffset(const mz_zip_archive_file_stat& fileStat) const;
+ public:
+  struct FileStatSlim {
+    uint16_t method;             // Compression method
+    uint32_t compressedSize;     // Compressed size
+    uint32_t uncompressedSize;   // Uncompressed size
+    uint32_t localHeaderOffset;  // Offset of local file header
+  };
+
+  struct ZipDetails {
+    uint32_t centralDirOffset;
+    uint16_t totalEntries;
+    bool isSet;
+  };
+
+ private:
+  const std::string& filePath;
+  File file;
+  ZipDetails zipDetails = {0, 0, false};
+  std::unordered_map<std::string, FileStatSlim> fileStatSlimCache;
+
+  bool loadFileStatSlim(const char* filename, FileStatSlim* fileStat);
+  long getDataOffset(const FileStatSlim& fileStat);
+  bool loadZipDetails();
 
  public:
-  explicit ZipFile(std::string filePath);
-  ~ZipFile() { mz_zip_reader_end(&zipArchive); }
-  bool getInflatedFileSize(const char* filename, size_t* size) const;
-  uint8_t* readFileToMemory(const char* filename, size_t* size = nullptr, bool trailingNullByte = false) const;
-  bool readFileToStream(const char* filename, Print& out, size_t chunkSize) const;
+  explicit ZipFile(const std::string& filePath) : filePath(filePath) {}
+  ~ZipFile() = default;
+  // Zip file can be opened and closed by hand in order to allow for quick calculation of inflated file size
+  // It is NOT recommended to pre-open it for any kind of inflation due to memory constraints
+  bool isOpen() const { return !!file; }
+  bool open();
+  bool close();
+  bool loadAllFileStatSlims();
+  bool getInflatedFileSize(const char* filename, size_t* size);
+  // Due to the memory required to run each of these, it is recommended to not preopen the zip file for multiple
+  // These functions will open and close the zip as needed
+  uint8_t* readFileToMemory(const char* filename, size_t* size = nullptr, bool trailingNullByte = false);
+  bool readFileToStream(const char* filename, Print& out, size_t chunkSize);
 };