st: add anysize patch

> By default, st's window size always snaps to the nearest multiple of
the character size plus a fixed inner border (set with borderpx in
config.h). When the size of st does not perfectly match the space
allocated to it (when using a tiling WM, for example), unsightly gaps
will appear between st and other apps, or between instances of st.
>
> This patch allows st to resize to any pixel size, makes the inner
border size dynamic, and centers the content of the terminal so that the
left/right and top/bottom borders are balanced. With this patch, st on a
tiling WM will always fill the entire space allocated to it.

https://st.suckless.org/patches/anysize

nix/overlays/default.nix

@@ -22,6 +22,7 @@
     st = prev.st.override {
       patches = [
         "${self}/patches/st/change-font.patch"
+        "${self}/patches/st/st-anysize-20220718-baa9357.diff"
       ];
     };
   };