chore: updates

* Update `run` tasks to use the Nix Flake instead of Docker.
* Output PDFs into a `dist` directory and name them as the talk name.
* Move the stylesheets into a common place.

flake.nix

@@ -12,7 +12,11 @@
         formatter = pkgs.nixpkgs-fmt;
 
         devshells.default = {
-          packages = with pkgs; [ python310Packages.rst2pdf ];
+          packages = with pkgs; [
+            pdfpc
+            python310Packages.rst2pdf
+            tree
+          ];
         };
       };
     };