fix compile error with gcc 13

The result of bit_width is an integer, and that can't be used
with bit_ceil. Adds an extra cast to make sure the type is
correct.

Fixes #3.

include/pareas/lpg/render_util.hpp

@@ -9,7 +9,7 @@
 namespace pareas {
     template <typename T>
     constexpr T int_bit_width(T x) {
-        auto width = std::max(T{8}, std::bit_ceil(std::bit_width(x)));
+        auto width = std::max(T{8}, std::bit_ceil(static_cast<T>(std::bit_width(x))));
         // This should only happen if there are a LOT of rules anyway.
         assert(width <= 64);
         return width;