Update dependencies and docs for gatsby theme

packages/gatsby-theme/README.md

@@ -15,7 +15,9 @@ module.exports = {
 }
 ```
 
-Add MDX Decks to the `src/decks/` directory.
+Add MDX Decks to the `src/decks/` directory. The filename will be used for the route of that deck.
+
+**/src/decks/hello.mdx**
 
 ```mdx
 # Hello!
@@ -29,6 +31,8 @@ Add MDX Decks to the `src/decks/` directory.
 
 Slide layout components must be rendered inline, _not_ using the default export syntax.
 
+**/src/decks/hello.mdx**
+
 ```mdx
 import Layout from './my-layout'
 

packages/gatsby-theme/gatsby-config.js

@@ -19,7 +19,7 @@ const themeConfig = (opts = {}) => {
         },
       },
       mdx && {
-        resolve: 'gatsby-mdx',
+        resolve: 'gatsby-plugin-mdx',
         options: {
           extensions: ['.mdx', '.md'],
           remarkPlugins,

packages/gatsby-theme/package.json

@@ -24,9 +24,9 @@
     "@mdx-js/mdx": "^1.0.1",
     "@mdx-js/react": "^1.0.1",
     "debug": "^4.1.1",
-    "gatsby-mdx": "^0.6.1",
     "gatsby-plugin-compile-es6-packages": "^1.1.0",
     "gatsby-plugin-emotion": "^4.0.6",
+    "gatsby-plugin-mdx": "^1.0.6",
     "gatsby-source-filesystem": "^2.0.29",
     "lodash.get": "^4.4.2",
     "mkdirp": "^0.5.1",