adding demo video and feature list

Author: codepo8

explainers/JSONViewer/explainer.md

@@ -19,17 +19,36 @@ When navigating to an HTML document, and selecting "view source" you get a colou
 
 We propose to replace tha basic JSON view with a colour-coded, collapsible and expandable one.
 
-![JSON in browser as a colour-coded, collapsible tree](colour-coded.png)
+![JSON in browser as a colour-coded, collapsible tree](json-viewer.gif)
 
-We are currently investigating the overall browser performance impact of this, which is why the first implementation will be basic.
+We are currently investigating the overall browser performance impact of this, which is why the first implementation is what is shown in the screencast above.
 
 ### Goals 
 
 As JSON files are data structures and users want to drill down into the data and analyse it in detail. This is a first step in this direction. In subsequent iterations we want to add more functionality like displaying header data and a raw view, saving and copying data and filtering the information.
 
 ### Usage 
 
-This functionality will trigger automatically when the browser navigates to a JSON file on the web or the user opens a local one.
+This functionality will trigger automatically when the browser navigates to a JSON file on the web or the user opens a local one. Once we add more features you will also be able to interact with the JSON data in more detail.
+
+### Feature release plan
+
+**Current:** JSON is being displayed as a collapsible tree with line numbers and colour coding in dark and light themes
+
+Upcoming features in delivery order: 
+
+* Get a "slow" warning when the JSON is too big to render and an option to show it as plain text instead
+* Get an "invalid" warning when the JSON payload is invalid
+* Switch between the expandable tree view and the raw text view
+* Copy the JSON payload with a button
+* Download the JSON payload with a button
+* Search/filter the JSON
+* Expand and collapse all the nodes in the document
+* Choose to display JSON in table format for array data that can be sorted/filtered
+* Large JSON payloads will load the first 500K and then offer to stream the rest
+* Choose to inherit themes from DevTools
+* Set Raw or Tree display as a default
+*  Open JSON in Network Console
 
 ## Feedback
 Have feedback? We want to hear it! *[Issue #87](https://github.com/MicrosoftEdge/DevTools/issues/87)* tracks community feedback on this explainer.