Generic Viem HaLo account provider (#444)

docs/viem-account.md

@@ -0,0 +1,25 @@
+# Using HaLo with Viem
+
+```
+import {createViemHaloAccount} from "@arx-research/libhalo/api/common";
+import {execHaloCmdWeb} from '@arx-research/libhalo/api/web';
+import {HaloResSign, HexString} from "@arx-research/libhalo/types";
+
+const HALO_KEY_NO = 8;
+const HALO_PASSWORD = "000000";
+
+async function haloSignDigest(address: Hex, digest: HexString): Promise<HaloResSign> {
+    return await execHaloCmdWeb({
+        digest,
+        keyNo: HALO_KEY_NO,
+        password: HALO_PASSWORD,
+    })
+}
+
+const account = createViemHaloAccount(
+    address,
+    async (digest: string): Promise<HaloResSign> => await haloSignDigest(address, digest)
+)
+
+// the "account" is ready to be used with Viem wallet/public clients
+```