patterns: Added AppleSingle, AppleDouble, CHD, TARC patterns (#431)

* Commit patterns I've collected

- AppleSingle/AppleDouble pattern, used for macOS resource forks.
- MAME CHD file format, currently only supports v5.
- KEX Engine proprietary TARC format, used by various Nightdive games.

* Add to README

patterns/chd.hexpat

@@ -0,0 +1,105 @@
+#pragma author Lexi Mayfield
+#pragma description MAME Compressed Hunks of Data
+#pragma endian big
+
+fn CHD_MAKE_TAG(char a, char b, char c, char d) {
+    return (u32(u8(a)) << 24) |
+           u32(u8((b)) << 16) |
+           u32(u8((c)) << 8) |
+            u32(u8(d));
+};
+
+enum CHDv5_CODEC : u32 {
+    NONE = 0,
+    ZLIB = CHD_MAKE_TAG('z','l','i','b'),
+    ZSTD = CHD_MAKE_TAG('z','s','t','d'),
+    LZMA = CHD_MAKE_TAG('l','z','m','a'),
+    HUFFMAN = CHD_MAKE_TAG('h','u','f','f'),
+    FLAC = CHD_MAKE_TAG('f','l','a','c'),
+    CD_ZLIB = CHD_MAKE_TAG('c','d','z','l'),
+    CD_ZSTD = CHD_MAKE_TAG('c','d','z','s'),
+    CD_LZMA = CHD_MAKE_TAG('c','d','l','z'),
+    CD_FLAC = CHD_MAKE_TAG('c','d','f','l'),
+    AVHUFF = CHD_MAKE_TAG('a','v','h','u'),
+};
+
+enum CHDv5_METADATA_TAG : u32 {
+    CHDMETATAG_WILDCARD = 0,
+    HARD_DISK_METADATA_TAG = CHD_MAKE_TAG('G','D','D','D'),
+    HARD_DISK_IDENT_METADATA_TAG = CHD_MAKE_TAG('I','D','N','T'),
+    HARD_DISK_KEY_METADATA_TAG = CHD_MAKE_TAG('K','E','Y',' '),
+    PCMCIA_CIS_METADATA_TAG = CHD_MAKE_TAG('C','I','S',' '),
+    CDROM_OLD_METADATA_TAG = CHD_MAKE_TAG('C','H','C','D'),
+    CDROM_TRACK_METADATA_TAG = CHD_MAKE_TAG('C','H','T','R'),
+    CDROM_TRACK_METADATA2_TAG = CHD_MAKE_TAG('C','H','T','2'),
+    GDROM_OLD_METADATA_TAG = CHD_MAKE_TAG('C','H','G','T'),
+    GDROM_TRACK_METADATA_TAG = CHD_MAKE_TAG('C','H','G','D'),
+    DVD_METADATA_TAG = CHD_MAKE_TAG('D','V','D',' '),
+    AV_METADATA_TAG = CHD_MAKE_TAG('A','V','A','V'),
+    AV_LD_METADATA_TAG = CHD_MAKE_TAG('A','V','L','D'),
+};
+
+struct CHDv5UncompressedMap {
+    u32 offset;
+};
+
+struct CHDv5CompressedMapEntry {
+    u8 compression;
+    u24 complength;
+    u48 offset;
+    u16 crc;
+};
+
+struct CHDv5CompressedMap {
+    u32 length;
+    u48 datastart;
+    u16 crc;
+    u8 lengthbits;
+    u8 hunkbits;
+    u8 parentunitbits;
+    u8 reserved;
+};
+
+struct CHDv5MetadataEntry {
+    CHDv5_METADATA_TAG metatag;
+    u8 flags;
+    u24 length;
+    u64 next;    
+    char entry[length];
+    
+    if (next != 0) {
+        CHDv5MetadataEntry nextMeta @ next;
+    }
+};
+
+struct CHDv5 {
+    CHDv5_CODEC compressors[4];
+    u64 logicalbytes;
+    u64 mapoffset;
+    u64 metaoffset;
+    u32 hunkbytes;
+    u32 unitbytes;
+    u8 rawsha1[20];
+    u8 sha1[20];
+    u8 parentsha1[20];
+    
+    if (compressors[0] == CHDv5_CODEC::NONE) {
+        CHDv5UncompressedMap map @ mapoffset;
+    } else {
+        CHDv5CompressedMap map @ mapoffset;
+    }
+    
+    CHDv5MetadataEntry meta @ metaoffset;
+};
+
+struct CHD {
+    char tag[8];
+    u32 length;
+    u32 version;
+    
+    if (version == 5) {
+        CHDv5 chd;
+    }
+};
+
+CHD chd @ 0x00;