fix: use addModule() so this can be imported as a module (#9)

build.zig

@@ -4,11 +4,8 @@ pub fn build(b: *std.Build) void {
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
 
-    _ = b.addStaticLibrary(.{
-        .name = "zig-stable-array",
+    _ = b.addModule("zig-stable-array", .{
         .root_source_file = b.path("stable_array.zig"),
-        .target = target,
-        .optimize = optimize,
     });
 
     const lib_unit_tests = b.addTest(.{