docs: document installation and usage

Author: alevito

README.md

@@ -4,6 +4,25 @@ WebAssembly module for decrypting Zcash shielded transactions.
 
 ## Getting Started
 
+### Installation
+```bash
+# npm
+npm install -s @ledger/zcash-decrypt
+
+# pnpm
+pnpm add @ledger/zcash-decrypt
+```
+
+### Usage
+
+```typescript
+import { decrypt_tx } from "@ledgerhq/zcash-decrypt";
+
+const decrypted = decrypt_tx(rawHexTransaction, viewingKey);
+```
+
+## Developing
+
 ### Requirements
 
 ```bash

package.json

@@ -3,6 +3,12 @@
   "collaborators": [
     "Alessandro Vito <alessandro.vito-ext@ledger.fr>"
   ],
+  "keywords": [
+    "Ledger",
+    "zec",
+    "zatoshi",
+    "ZCash"
+  ],
   "version": "0.1.0",
   "license": "MIT AND Apache-2.0",
   "repository": {