feat(users/kranzes): add wasm-hello-world

This can be used as a reference for how to build a wasm project with
crate2nix.

Change-Id: Ib4d0db6bf24d8f1dec4734d5f1e8de19212a54cd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11859
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

users/kranzes/wasm-hello-world/default.nix

@@ -0,0 +1,15 @@
+{ pkgs, lib, ... }:
+
+(pkgs.pkgsCross.wasm32-unknown-none.callPackage ./Cargo.nix { }).rootCrate.build.overrideAttrs (oldAttrs: {
+  installPhase = ''
+    ${lib.getExe pkgs.wasm-bindgen-cli} \
+      --target web \
+      --out-dir $out \
+      --out-name ${oldAttrs.crateName} \
+      --no-typescript \
+      target/lib/${oldAttrs.crateName}-${oldAttrs.metadata}.wasm
+
+      mv src/*.html $out
+  '';
+})
+