Add tshm package

Stripping breaks the binary like so:
  NixOS/patchelf#99

editor.nix

@@ -7,6 +7,8 @@ let
     sha256 = "0gpyvzy0yndjaq0aifzjm1c453ar9ma4610v6q5zhbp5vs4padlg";
   }) {};
 
+  tshm = pkgs.callPackage ./pkg/tshm.nix {};
+
   exrc-vim = pkgs.vimUtils.buildVimPlugin {
     name = "exrc.vim";
     src = builtins.fetchTarball {
@@ -117,6 +119,7 @@ in {
       # Tools w/ language server interop
       hlint
       stylish-haskell
+      tshm
     ];
   };
 }

pkg/tshm.nix

@@ -0,0 +1,32 @@
+{ fetchurl, lib, pkgs, stdenv }:
+
+stdenv.mkDerivation rec {
+  pname = "tshm";
+  version = "0.4.0";
+
+  src = fetchurl {
+    url = "https://github.com/samhh/tshm/releases/download/${version}/tshm-linux-amd64";
+    sha256 = "03nnhmplmn2mqibqclyr28dhh1v0f4dn18k4rnbvc9xy2l4k32xf";
+  };
+
+  dontUnpack = true;
+  dontStrip = true;
+
+  installPhase = ''
+    mkdir -p $out/bin/
+    cp $src $out/bin/tshm
+    chmod +x $out/bin/tshm
+  '';
+
+  preFixup =
+    let libPath = with pkgs; lib.makeLibraryPath [ gmp ];
+    in ''
+      patchelf --set-interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" --set-rpath ${libPath} $out/bin/tshm
+    '';
+
+  meta = {
+    homepage = "https://github.com/samhh/tshm";
+    description = "A parser and formatter for TypeScript declarations that outputs HM-style type signatures.";
+    license = lib.licenses.mit;
+  };
+}