make web version work, add dockerfile

devenv.nix

@@ -1,5 +1,4 @@
-{ pkgs, ... }:
-{
+{pkgs, ...}: {
   android = {
     enable = true;
     emulator.enable = false;
@@ -39,4 +38,15 @@
     # Needed by flutter_secure_storage
     libsecret.dev
   ];
+
+  processes.web-server = {
+    exec = "python -m http.server 8080 -d build/web";
+  };
+
+  scripts = {
+    web-to-container.exec = ''
+      flutter build web --release
+      docker build -t sheetless .
+    '';
+  };
 }