patterns: Add a pattern for Roblox .pack files (#435)

* Added the .pack format

* Clarified some fields by changing the naming

README.md

@@ -128,6 +128,7 @@ Everything will immediately show up in ImHex's Content Store and gets bundled wi
 | NTFS | | [`patterns/fs/ntfs.hexpat`](patterns/fs/ntfs.hexpat) | NTFS (NT File System) |
 | OGG | `audio/ogg` | [`patterns/ogg.hexpat`](patterns/ogg.hexpat) | OGG Audio format |
 | ORP / ORS | | [`patterns/orp.hexpat`](patterns/orp.hexpat) | OpenRGB profile format |
+| PACK | | [`patterns/roblox_pack.hexpat`](patterns/roblox_pack.hexpat) | Roblox shader archive format |
 | PAK | | [`patterns/xgspak.hexpat`](patterns/xgspak.hexpat) | Exient XGS Engine Pak files |
 | PCAP | `application/vnd.tcpdump.pcap` | [`patterns/pcap.hexpat`](patterns/pcap.hexpat) | pcap header and packets |
 | PcapNG | `application/vnd.tcpdump.pcap` | [`patterns/pcapng.hexpat`](patterns/pcapng.hexpat) | pcapng header and packets |

patterns/roblox_pack.hexpat

@@ -0,0 +1,33 @@
+#pragma author marduk.ru
+#pragma description Roblox .pack shader archive format
+#pragma magic [ 52 42 58 53 ] @ 0x00
+
+import std.string;
+import hex.core;
+import type.magic;
+
+struct Header {
+    type::Magic<"RBXS"> magic;
+    u32 fileCount;
+};
+
+struct FileIndex {
+    char name[0x40];
+    u128 md5Hash;
+    u32  offset;
+    u32  size;
+    u64  reserved;
+    
+    u8 file[size] @ offset;
+    
+    #ifdef __IMHEX__
+    hex::core::add_virtual_file(name, file);
+    #endif
+} [[name(name)]];
+
+struct RBXPack {
+    Header header;
+    FileIndex files[header.fileCount];
+};
+
+RBXPack pack @ 0x0;