Add files via upload

sppm-js/README.md

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+# SPPM JavaScript tools
+
+Dependency-free ES module for Node.js 20+ and modern browsers.
+
+```js
+import { readSppm, getSppmMetadata, getSppmThumbnail, SppmPlayer } from "./index.js";
+
+const note = await readSppm("my-note.sppm");
+console.log(await getSppmMetadata("my-note.sppm"));
+const { width, height, data } = await getSppmThumbnail("my-note.sppm");
+const player = new SppmPlayer(document.querySelector("canvas"), note);
+await player.play(); // starts at the first frame; includes BGM and frame-cued effects
+```
+
+`readSppm` validates the container and CRCs. Current Ed25519 `SPP3` signatures
+are verified through WebCrypto when supported. Legacy `SPPS` HMAC files are
+reported as unverified unless `legacyHmacKey` is provided. This module reads and
+renders notes; it does not create or sign SPPM files. The thumbnail is RGBA with
+a solid white background by default and uses the note's cover frame.