feat(tvix/docs): switch to mdbook

Some of the docs are still outdated (like architecture and drv path
inconsistencies).

Change-Id: I7a6afceb008ef4cd19a764dd6c637b39fa842a2e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11072
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: edef <edef@edef.eu>

web/bubblegum/examples/default.nix

@@ -4,7 +4,6 @@ let
 
   scripts = [
     ./hello.nix
-    ./derivation-svg.nix
     (substituteAll {
       src = ./blog.nix;
       # by making this a plain string this