patterns: Added Password Safe Version 3 pattern (#266)

* Add password safe V3

* Added description pragma

---------

Co-authored-by: Nik <werwolv98@gmail.com>

README.md

@@ -96,6 +96,7 @@ Everything will immediately show up in ImHex's Content Store and gets bundled wi
 | PNG  | `image/png` | [`patterns/png.hexpat`](patterns/png.hexpat) | PNG image files |
 | PRODINFO | | [`patterns/prodinfo.hexpat`](patterns/prodinfo.hexpat) | Nintendo Switch PRODINFO |
 | Protobuf | | [`patterns/protobuf.hexpat`](patterns/protobuf.hexpat) | Google Protobuf encoding |
+| psafe3 | | [`patterns/psafe3.hexpat`](patterns/psafe3.hexpat`) | Password Safe V3 |
 | PyInstaller | | [`patterns/pyinstaller.hexpat`](patterns/pyinstaller.hexpat) | PyInstaller binray files |
 | PYC | | [`patterns/pyc.hexpat`](patterns/pyc.hexpat) | Python bytecode files |
 | QBCL | | [`patterns/qbcl.hexpat`](patterns/qbcl.hexpat) | Qubicle voxel scene project file |

patterns/psafe3.hexpat

@@ -0,0 +1,33 @@
+// Password Safe V3
+// Only a small part of the file is unencrypted.
+
+#pragma endian little
+#pragma description Password Safe V3
+
+import std.mem;
+import std.sys;
+
+struct Prologue {
+    u8 SALT[32];
+    u32 ITER;
+    u8 HPP[32] [[name("H(P')")]];
+    u8 B1[16];
+    u8 B2[16];
+    u8 B3[16];
+    u8 B4[16];
+    u8 IV[16];
+};
+
+struct EOF {
+    u8 HMAC[32];
+};
+
+char magic[4] @ 0x00;
+std::assert(magic == "PWS3", "Invalid file: bad tag!");
+char marker[16] @ std::mem::size() - 48;
+std::assert(marker == "PWS3-EOFPWS3-EOF", "Invalid file: bad end marker!");
+
+Prologue prologue @ 0x04;
+u8 HMAC[32] @ std::mem::size() - 32;
+
+EOF eof @ std::mem::size() - 48;