[#861] Add instructions to install prettier to code editor

Author: catarak

developer_docs/installation.md

@@ -27,11 +27,11 @@ _Note_: The installation steps assume you are using a Unix-like shell. If you ar
 7. `$ cp .env.example .env`
 8. (Optional) Update `.env` with necessary keys to enable certain app behaviors, i.e. add Github ID and Github Secret if you want to be able to log in with Github.
 9. Run `$ npm run fetch-examples` to download the example sketches into a user called 'p5'. Note that you need to configure your GitHub Credentials, which you can do by following the [Github API Configuration](#github-api-configuration) section.
-
-10. `$ npm start`
-11. Navigate to [http://localhost:8000](http://localhost:8000) in your browser
-12. Install the [React Developer Tools](https://chrome.google.com/webstore/detail/react-developer-tools/fmkadmapgofadopljbjfkapdkoienihi?hl=en)
-13. Open and close the Redux DevTools using `ctrl+h`, and move them with `ctrl+w`
+10. Enable Prettier in your text editor by following [this guide](https://prettier.io/docs/en/editors.html).
+11. `$ npm start`
+12. Navigate to [http://localhost:8000](http://localhost:8000) in your browser
+13. Install the [React Developer Tools](https://chrome.google.com/webstore/detail/react-developer-tools/fmkadmapgofadopljbjfkapdkoienihi?hl=en)
+14. Open and close the Redux DevTools using `ctrl+h`, and move them with `ctrl+w`
 
 ## Docker Installation
 
@@ -49,20 +49,20 @@ Note that this takes up a significant amount of space on your machine. Make sure
 4. `$ cp .env.example .env`
 5. (Optional) Update `.env` with necessary keys to enable certain app behavoirs, i.e. add Github ID and Github Secret if you want to be able to log in with Github.
 6. `$ docker-compose -f docker-compose-development.yml run --rm app npm run fetch-examples` -  note that you need to configure your GitHub Credentials, which you can do by following the [Github API Configuration](#github-api-configuration) section.
-
+7. Enable Prettier in your text editor by following [this guide](https://prettier.io/docs/en/editors.html).
 
 Now, anytime you wish to start the server with its dependencies, you can run:
 
-7. `$ docker-compose -f docker-compose-development.yml up`
-8. Navigate to [http://localhost:8000](http://localhost:8000) in your browser
+8. `$ docker-compose -f docker-compose-development.yml up`
+9. Navigate to [http://localhost:8000](http://localhost:8000) in your browser
 
 To open a terminal/shell in the running Docker server (i.e. after `docker-compose up` has been run):
 
-9. `$ docker-compose -f docker-compose-development.yml exec app bash -l`
+10. `$ docker-compose -f docker-compose-development.yml exec app bash -l`
 
 If you don't have the full server environment running, you can launch a one-off container instance (and have it automatically deleted after you're done using it):
 
-10. `$ docker-compose -f docker-compose-development.yml run app --rm bash -l`
+11. `$ docker-compose -f docker-compose-development.yml run app --rm bash -l`
 
 ## S3 Bucket Configuration