Updates README.md with Starbucks Careers site (react-static#1032)

Adds Starbucks Sites Built, with link to source.

<!--- Provide a general summary of your changes in the Title above -->

## Description
<!--- Describe your changes in detail -->

## Changes/Tasks
<!--- Add your changes or task as points (descriptions can be TL;DR) -->
- [ ] Changed code

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
<!--- If it fixes an open issue, please link to the issue here. -->

## Screenshots (if appropriate):
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## Types of changes
<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
- [ ] Refactoring/add tests (refactoring or adding test which isn't a fix or add a feature)
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

## Checklist:
<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
- [ ] My change requires a change to the documentation.
  - [ ] I have updated the documentation accordingly.
- [ ] My changes have tests around them

Author: Cher Scarlett

README.md

@@ -46,6 +46,8 @@ React-Static is a fast, lightweight, and powerful framework for building static-
 
 - [HeadlessCMS.org](https://headlesscms.org) ([source](https://github.com/netlify/headlesscms.org))
 - [StaticGen.com](https://staticgen.com) ([source](https://github.com/netlify/staticgen))
+- [Starbucks: Careers Hub](https://www.starbucks.com/careers/)([source](https://twitter.com/codehitchhiker/status/1097558315020832774))
+- [Intuit Turbo](http://turbo.com)
 - [Nozzle.io](https://nozzle.io) ([source](https://github.com/nozzle/nozzle.io))
 - [Timber.io](https://timber.io)
 - [TannerLinsley.com](https://tannerlinsley.com) ([source](https://github.com/tannerlinsley/tannerlinsley.com))
@@ -61,7 +63,6 @@ React-Static is a fast, lightweight, and powerful framework for building static-
 - [NYC Vintage Map](https://nycvintagemap.com)
 - [Eldar Labs - Utilities and Productivity Tools](https://eldarlabs.com)
 - [Dan Webb - Personal Website](https://danwebb.co) ([source](https://github.com/DanWebb/danwebb.co))
-- [Intuit Turbo](http://turbo.com)
 - [Messenger Corp. client asset ordering](http://chartwells.messengercorp.com/)
 - [Digital Neighborhood watch service](https://neighborhoodwatch.io/)
 - [Carmen Marcos Art - Artist Portfolio](http://carmen-marcos.art/) ([source](https://github.com/rafacm/carmen-marcos-art-portfolio))