add encrypting for save files

add libhydrogen for encrypting and decrypting

#9

libs/libhydrogen/build.zig

@@ -0,0 +1,32 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{ .preferred_optimize_mode = .ReleaseSmall });
+
+    const mod = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libc = true,
+        .strip = true,
+    });
+
+    mod.addCSourceFile(.{
+        .file = b.path("hydrogen.c"),
+    });
+
+    const lib = b.addLibrary(.{
+        .name = "hydrogen",
+        .linkage = .static,
+        .root_module = mod,
+    });
+
+    b.installArtifact(lib);
+
+    _ = b.addModule("libhydrogen", .{
+        .root_source_file = b.path("hydrogen.c"),
+        .target = target,
+        .optimize = optimize,
+        .link_libc = true,
+    });
+}