misc: rework shell.nix, reformat, ditch .editorconfig

shell.nix

@@ -1,19 +1,12 @@
 let
-  nixpkgs = fetchTarball {
-    name = "nixpkgs";
-    url = "https://github.com/NixOS/nixpkgs/archive/refs/tags/21.05.tar.gz";
-    sha256 = "1ckzhh24mgz6jd1xhfgx0i9mijk6xjqxwsshnvq789xsavrmsc36";
-  };
-  pkgs = import nixpkgs {};
+  pkgs = import <nixpkgs> { };
 in
-  pkgs.mkShell {
-    name = "env";
-    buildInputs = with pkgs; [
-      nodejs
-    ];
-    shellHook = ''
-PATH=./node_modules/.bin:$PATH
-command -v tree-sitter >/dev/null 2>&1 || npm install tree-sitter-cli@0.20.6
-    '';
-  }
+pkgs.mkShell {
+  name = "env";
+  buildInputs = with pkgs; [
+    nodejs
+    tree-sitter
+    emscripten
+  ];
+}