Add README for the VS Code extension

Author: shadaj

packages/apollo-vscode/README.md

@@ -0,0 +1,68 @@
+# Apollo GraphQL VS Code
+
+## The Aim
+
+An all-in-one experience for developing applications with GraphQL.
+
+- IDE completion and feedback everywhere
+- Run queries you write without leaving the editor
+- Provide performance statistics next to your query definitions
+
+![Code completing queries](./images/variable-argument-completion.gif)
+![Running a query with variables](./images/query-with-vars.gif)
+![Viewing Engine statistics](./images/engine-stats.png)
+
+## Features
+
+- Loads your GraphQL schemas and queries automatically from an [Apollo Config](../apollo-cli/config.md) file
+- Adds syntax highlighting for GraphQL files and `gql` templates inside JavaScript files
+- Code-completes fields, arguments, types, and variables in your queries
+- Lets you run queryies, mutations, and subscriptions within the IDE with code-completion for variables
+- Displays performance statistics from [Apollo Engine](https://www.apollographql.com/engine) inline with your queries
+- Jump-to-definition for fragments and schema types
+- Detects fragment references and shows them next to definitions
+
+## How to get it?
+
+Open up VS Code and search for the extension "Apollo".
+
+## How to get it set up?
+
+The extension searches for [Apollo Config](../apollo-cli/config.md) definitions in `package.json` or `apollo.config.js` files. To set up a basic endpoint and queries defined in `.tsx` files, a config file would look like.
+
+```js
+// package.json
+
+{
+  ...,
+  "apollo": {
+    "schemas": {
+      "mainSchema": {
+        "endpoint": "http://localhost:4000/graphql"
+      }
+    },
+    "queries": [
+      {
+        "schema": "mainSchema",
+        "includes": [ "**/*.tsx" ]
+      }
+    ]
+  }
+}
+```
+
+## How do we run queries?
+
+The extension enables query execution when an `endpoint` is specified for the schema you are targeting. When you hit `Run query/mutations/subscription`, the extension will open a variables editor if there are any variables defined or directly run the query otherwise.
+
+Queries and mutations are executed with a default [Apollo Link HTTP](https://www.apollographql.com/docs/link/links/http.html) configured to run queries against the specified endpoint. Subscriptions are handled with [Apollo Link WS](https://www.apollographql.com/docs/link/links/ws.html) configured to run against the `subscriptions` key in your schema or your endpoint with `http` replaced by `ws` if the key is not defined.
+
+## Troubleshooting
+
+### Extension not starting correctly? Check the logs!
+
+If you're having trouble with the extension not launching or not detecting your configuration files, you can check the language server logs.
+
+1.  Open the VS Code output tab from the bottom of your editor
+2.  Switch the output view to "Apollo GraphQL"
+3.  Check the logs and report any bugs you find!