feat: add svelte

the functionality for a svelte package
isn't here yet though :(

templates/svelte/flake/derivation.nix

@@ -0,0 +1,12 @@
+{ mkYarnPackage }:
+let
+  pname = "svelte-example";
+  version = "0.1.0";
+in
+mkYarnPackage {
+  inherit pname version;
+  src = ../.;
+  yarnLock = ../yarn.lock;
+  yarnNix = ../yarn.nix;
+  packageJSON = ../package.json;
+}

templates/svelte/flake/devshell.nix

@@ -0,0 +1,22 @@
+{
+  mkShell,
+  nodePackages_latest,
+  typescript,
+  yarn2nix,
+  nixd,
+}:
+mkShell {
+  name = "svelte";
+  packages = builtins.attrValues {
+    inherit (nodePackages_latest)
+      nodejs
+      npm
+      yarn
+      typescript-language-server
+      prettier
+      svelte-language-server
+      eslint
+      ;
+    inherit yarn2nix typescript nixd;
+  };
+}