Docs: Update readme

Author: erodewald

README.md

@@ -1,2 +1,86 @@
 # firestore-context-store-nodejs
-Stores SmartApp configuration and auth tokens for use in app-initiated calls
+
+<p>
+<a href="https://npmjs.org/package/@smartthings/firestore-context-store"><img src="https://badge.fury.io/js/@smartthings/firestore-context-store.svg"></a>
+<a href="https://circleci.com/gh/SmartThingsCommunity/firestore-context-store-nodejs.svg?style=svg"><img src="https://circleci.com/gh/SmartThingsCommunity/firestore-context-store-nodejs.svg?style=svg"></a>
+<a href="https://david-dm.org/SmartThingsCommunity/firestore-context-store-nodejs"><img src="https://david-dm.org/SmartThingsCommunity/firestore-context-store-nodejs.svg?theme=shields.io"></a>
+<a href="https://codecov.io/gh/SmartThingsCommunity/firestore-context-store-nodejs"><img src="https://codecov.io/gh/SmartThingsCommunity/firestore-context-store-nodejs/branch/master/graph/badge.svg" /></a>
+</p>
+
+> Stores SmartApp configuration and auth tokens for use in app-initiated calls
+
+Used by the [SmartApp SDK](https://github.com/SmartThingsCommunity/smartapp-sdk-nodejs) to store IDs and access tokens for an installed instance of a SmartApp
+and retrieves that information for use in asynchronous API calls. The use of a context store
+is only needed when SmartApps have to call the SmartThings API in response to external
+events. SmartApps that only response to lifecycle events from the SmartThings platform
+will automatically have the proper context without the app having to store it.
+
+The context stored by this module consists of the following data elements:
+
+- **installedAppId**: the UUID of the installed app instance. This is the primary key of the table.
+- **locationId**: the UUID of the location in which the app is installed
+- **authToken**: the access token used in calling the API
+- **refreshToken**: the refresh token used in generating a new access token when one expires
+- **clientId**: the SmartApp's client ID, used in generating a new access token
+- **clientSecret**: the SmartApp's client secret, used in generating a new access token
+- **config**: the current installed app instance configuration, i.e. selected devices, options, etc.v
+
+## Installation
+
+```shell
+npm install @smartthings/firestore-context-store --save
+```
+
+## Usage
+
+### A note about usage
+
+This package currently targets initializing Cloud Firestore from your own server by using a Service Account. If you are hosted on something like [Firebase Cloud Functions](https://firebase.google.com/docs/functions/) or [Google Cloud Platform](https://cloud.google.com/), we don't currently support those methodologies – feel free to contribute!
+
+To use this module to add Firebase Cloud Firestore context storage to your SmartApp, you should:
+
+1. **Generate a service account**. We use the Firebase Admin SDK. Go to IAM & admin > Service accounts in the Cloud Platform Console. Generate a new private key and save the JSON file. Then use the file to initialize the SDK in the next step.
+
+1. **`require()` your Google Services service account JSON file.** Be certain that you don't ever commit this file to a public repository.
+
+1. **Create a context store instance** with the service account object and the document collection name and pass it to the SmartApp SDK object. For example, the following code:
+
+```javascript
+const smartapp = require('@smartthings/smartapp');
+const FirestoreDBContextStore = require('@smartthings/firestore-context-store');
+const serviceAccount = require('./googleservices-YOURAPPNAME-AND-ID.json')
+
+smartapp
+  .contextStore(new FirestoreDBContextStore(serviceAccount, 'installedapps'))
+  .configureI18n()
+  .page('mainPage', (page) => {
+    ...
+```
+
+This will use a document collection named `installedapps` to store documents as keyed by the `installedAppId` value.
+
+### Firebase Console
+
+From the Firebase Cloud Firestore console, you will see a new document collection with persisted contexts.
+
+![img](docs/example_console.png)
+
+## More about SmartThings
+
+If you are not familiar with SmartThings, we have
+[extensive on-line documentation](https://smartthings.developer.samsung.com/develop/index.html).
+
+To create and manage your services and devices on SmartThings, create an account in the
+[developer workspace](https://devworkspace.developer.samsung.com/).
+
+The [SmartThings Community](https://community.smartthings.com/c/developers/) is a good place share and
+ask questions.
+
+There is also a [SmartThings reddit community](https://www.reddit.com/r/SmartThings/) where you
+can read and share information.
+
+## License and Copyright
+
+Licensed under the [Apache License, Version 2.0](https://www.apache.org/licenses/LICENSE-2.0)
+
+Copyright 2019 SmartThings, Inc.