Add example & JSR tag

Author: NfNitLoop

README.md

@@ -1,3 +1,53 @@
-A TypeScript/JavaScript API client for [Diskuto].
+[![JSR Version]][JSR Link]
 
-[Diskuto]: https://github.com/diskuto/
+Diskuto API Client
+==================
+
+A TypeScript/JavaScript API client for [Diskuto REST API].
+
+Example
+-------
+
+Here's an example from [this blog post][1] of how to fetch and validate an `Item`
+using this API client:
+
+```typescript
+#!/usr/bin/env -S deno run --check -EN
+
+const baseUrl = `https://blog.nfnitloop.com`
+const userID = `A719rvsCkuN2SC5W2vz5hypDE2SpevNTUsEXrVFe9XQ7`
+const signature = `4sVxU7pVvUenEdG41BYJDZJfDBZBjBkLSF7dcGzpGMgtVLbZjTh6w5LzC4Rwjkk5SNyn57o3cfsvEbsZJkFELaW3`
+
+// Given these three things, we can validate that the content on the page
+// was in fact created by that user, and has not been modified.
+
+import {Client, Signature, UserID} from "jsr:@diskuto/client@0.10.0"
+const client = new Client({baseUrl})
+
+const bytes = await client.getItemBytes(userID, signature)
+if (bytes == null) {
+    throw new Error(`No such item on this server.`)
+}
+
+// Some helper types for working with cryptography:
+const uid = UserID.fromString(userID)
+const sig = Signature.fromString(signature)
+
+const valid = await sig.isValid(uid, bytes)
+if (!valid) {
+    throw new Error(`Invalid signature!`)
+}
+
+// OK, we have a valid signature for ... some bytes. But is that what's on the page?
+// We'll need to inspect the contents of those bytes to verify that the server isn't 
+// misrepresenting them:
+import { fromBinary, ItemSchema } from "jsr:@diskuto/client/types";
+const item = fromBinary(ItemSchema, bytes)
+console.log(item)
+```
+
+
+[Diskuto REST API]: https://github.com/diskuto/diskuto-api/tree/main/docs/rest_api
+[1]: https://blog.nfnitloop.com/u/A719rvsCkuN2SC5W2vz5hypDE2SpevNTUsEXrVFe9XQ7/i/33QiHdeD3sSiB5mWwSBJhpkjQEystr4nx9W8FFWWM1oWfCFMfDHpYuKMGJ6v8kmf2pHnnhL67Reg14jGRVoTyJ7Z/
+[JSR Version]: https://jsr.io/badges/@diskuto/client
+[JSR Link]: https://jsr.io/@diskuto/client