v0.2.1

Snapshot can now download or copy to clipboard — additive, non-breaking.

• snapshot() gains target ("blob" default · "download" · "clipboard") and
  filename: it captures, optionally delivers the PNG, and always returns the Blob.
• Toolbar: one camera button now offers both deliveries. ToolbarOptions.snapshot
  accepts { state, onClick } — onClick ("download" | "clipboard", default
  "download") is the plain-click delivery; the other runs on a modifier-click
  (Ctrl on PC/Linux, ⌘ on Mac). The string form (snapshot: "high") still works.
• Clipboard uses the async Clipboard API (needs a secure context — HTTPS/localhost;
  the click is the required user gesture).
• New export copyPng(blob); new SnapshotTarget / SnapshotDelivery types;
  ToolbarItem.onClick now receives the MouseEvent (for modifier keys).