feat(users/Profpatsch): set up a file watcher for tree sitter

Uses inotify to watch a file and print when it is modified, so we can
update the parser and display the sexp on the terminal.

Now the setup is good enough to start experiementing with queries on
the syntax tree.

Change-Id: I091587fc495ff627c79a69a52915aaaa8c51fcd2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2411
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

third_party/nixpkgs-exposed/exposed/default.nix

@@ -13,6 +13,7 @@
     avrlibc
     bashInteractive
     bat
+    bc
     buildBazelPackage
     buildFHSUserEnv
     buildGoModule
@@ -44,6 +45,7 @@
     emacsPackagesGen
     execline
     fd
+    fdtools
     fetchFromGitHub
     fetchgit
     fetchurl
@@ -87,9 +89,11 @@
     mkShell
     moreutils
     nano
+    ncurses
     nginx
     ninja
     nix
+    ocamlPackages
     openssh
     openssl
     overrideCC