Point to the VSCode marketplace in the readme (#134)

* Point to the VSCode marketplace in the readme

* Move instructions for building the VSCode extension to Hacking section

Author: cocreature

README.md

@@ -69,14 +69,8 @@ Once you have got `ghcide` working outside the editor, the next step is to pick
 
 ### Using with VS Code
 
-Install the VS code extension (see https://code.visualstudio.com/docs/setup/mac for details on adding `code` to your `$PATH`):
-
-1. `cd extension/`
-2. `npm ci`
-3. `npm run vscepackage`
-4. `code --install-extension ghcide-0.0.1.vsix`
-
-Now opening a `.hs` file should work with `ghcide`.
+You can install the VSCode extension from the [VSCode
+marketplace](https://marketplace.visualstudio.com/items?itemName=DigitalAssetHoldingsLLC.ghcide).
 
 ### Using with Emacs
 
@@ -171,6 +165,24 @@ Add this to your coc-settings.json (which you can edit with :CocConfig):
 Here's a nice article on setting up neovim and coc: [Vim and Haskell in
 2019](http://marco-lopes.com/articles/Vim-and-Haskell-in-2019/)
 
+## Hacking on ghcide
+
+To build and work on `ghcide` itself, you can use Stack or cabal, e.g.,
+running `stack test` will execute the test suite.
+
+### Building the extension
+
+For development, you can also the VSCode extension from this repository (see
+https://code.visualstudio.com/docs/setup/mac for details on adding
+`code` to your `$PATH`):
+
+1. `cd extension/`
+2. `npm ci`
+3. `npm run vscepackage`
+4. `code --install-extension ghcide-0.0.1.vsix`
+
+Now opening a `.hs` file should work with `ghcide`.
+
 ## History and relationship to other Haskell IDE's
 
 The code behind `ghcide` was originally developed by [Digital Asset](https://digitalasset.com/) as part of the [DAML programming language](https://github.com/digital-asset/daml). DAML is a smart contract language targeting distributed-ledger runtimes, based on [GHC](https://www.haskell.org/ghc/) with custom language extensions. The DAML programming language has [an IDE](https://webide.daml.com/), and work was done to separate off a reusable Haskell-only IDE (what is now `ghcide`) which the [DAML IDE then builds upon](https://github.com/digital-asset/daml/tree/master/compiler/damlc). Since that time, there have been various [non-Digital Asset contributors](https://github.com/digital-asset/ghcide/graphs/contributors), in addition to continued investment by Digital Asset. All contributions require a [Contributor License Agreement](https://cla.digitalasset.com/digital-asset/ghcide) that states you license the code under the [Apache License](LICENSE).