Package: Add build.zig to list of paths (#29)

Add missing `build.zig` file to list of exported paths. This fixes an
issue where projects depending on pgzx can not import the pgzx build
tools.

Author: urso

build.zig.zon

@@ -2,6 +2,7 @@
     .name = "pgzx",
     .version = "0.1.0",
     .paths = .{
+        "build.zig",
         "src",
     },
 }