Adding resolve.extentions to configuration sample

I think it makes sense to have it there, because people will pretty quickly run into `Module not found: Error: Can't resolve` and it is not easy to figure out the cause of this error by searching since it is very generic.
Besides, I've extended second configuration example with additional rule; it is easier to copy paste it that ways, which people will likely do.

Author: jurijsk

content/guides/webpack-and-typescript.md

@@ -57,15 +57,18 @@ module.exports = {
        test: /\.tsx?$/,
        loader: 'ts-loader',
        exclude: /node_modules/,
-     }
+     },
    ]
- }
+ }, 
+ resolve: {
+   extensions: ["*", ".tsx", ".ts", ".js"]
+ },
 };
 ```
 
 Here we specify our entry point to be __index.ts__ in our current directory, 
 an output file called __bundle.js__ 
-and our TypeScript loader that is in charge of compiling our TypeScript file to JavaScript.
+and our TypeScript loader that is in charge of compiling our TypeScript file to JavaScript. We also add `resolve.extensions` to insruct webpack what file extensions to use when resolving Typescript modules.
 
 ## Typescript loaders
 
@@ -111,8 +114,16 @@ module.exports = {
        test: /\.js$/,
        loader: "source-map-loader"
      },
+     {
+       enforce: 'pre',
+       test: /\.js$/,
+       use: "source-map-loader"
+     }
    ]
  },
+ resolve: {
+   extensions: ["*", ".tsx", ".ts", ".js"]
+ },
  devtool: 'inline-source-map',
 };
 ```
@@ -163,4 +174,4 @@ Here we declare a new module for svg by specifying any import that ends in __.sv
 If we wanted to be more explicit about this being a url we could define the type as string.
 
 This applies not only to svg but any custom loader you may want to use which includes css, scss, json or any other file you may wish to load in your project.
- 
+