Adds JSON package overview.

Author: Simon Prickett

packages/json/README.md

@@ -1,2 +1,80 @@
 # @node-redis/json
-The sources and docs for this package are in the main [node-redis](https://github.com/redis/node-redis) repo.
+
+This package provides support for the [RedisJSON](https://redisjson.io) module, which adds JSON as a native data type to Redis.  It extends the [Node Redis client](https://) to include functions for each of the RedisJSON commands.
+
+To use these extra commands, your Redis server must have the RedisJSON module installed.
+
+## Usage
+
+For a complete example, see [`managing-json.js`](https://github.com/redis/node-redis/blob/master/examples/managing-json.js) in the Node Redis examples folder.
+
+### Storing JSON Documents in Redis
+
+The [`JSON.SET`](https://oss.redis.com/redisjson/commands/#jsonset) command stores a JSON value at a given JSON Path in a Redis key.
+
+Here, we'll store a JSON document in the root of the Redis key "`mydoc`":
+
+```javascript
+import { createClient } from 'redis';
+
+...
+await client.json.set('noderedis:jsondata', '$', {
+  name: 'Roberta McDonald',
+  pets: [
+    {
+    name: 'Rex',
+    species: 'dog',
+    age: 3,
+    isMammal: true
+    },
+    {
+    name: 'Goldie',
+    species: 'fish',
+    age: 2,
+    isMammal: false
+    }      
+  ]
+});
+```
+
+For more information about RedisJSON's path syntax, [check out the documentation](https://oss.redis.com/redisjson/path/).
+
+### Retrieving JSON Documents from Redis
+
+With RedisJSON, we can retrieve all or part(s) of a JSON document using the [`JSON.GET`]() command and one or more JSON Paths.  Let's get the name and age of one of the pets:
+
+```javascript
+const results = await client.json.get('noderedis:jsondata', {
+  path: [
+    '.pets[1].name',
+    '.pets[1].age'
+  ]
+});
+```
+
+`results` will contain the following:
+
+```javascript
+ '.pets[1].name': 'Goldie', '.pets[1].age': 2 }
+```
+
+### Performing Atomic Updates on JSON Documents Stored in Redis
+
+RedisJSON includes commands that can atomically update values in a JSON document, in place in Redis without having to first retrieve the entire document.
+
+Using the [`JSON.NUMINCRBY`](https://oss.redis.com/redisjson/commands/#jsonnumincrby) command, we can update the age of one of the pets like this:
+
+```javascript
+await client.json.numIncrBy('noderedis:jsondata', '.pets[1].age', 1);
+```
+
+And we can add a new object to the pets array with the [`JSON.ARRAPPEND`](https://oss.redis.com/redisjson/commands/#jsonarrappend) command:
+
+```javascript
+ await client.json.arrAppend('noderedis:jsondata', '.pets', {
+    name: 'Robin',
+    species: 'bird',
+    age: 1,
+    isMammal: false
+  });
+```