Add Doist as sponsor (#435)

Author: runningcode

docs/index.md

@@ -18,15 +18,19 @@ Also read this [medium post](https://medium.com/walmartlabs/flank-smart-test-run
 
 ## Corporate Sponsors
 
-[Be the first to sponsor Fladle!](https://github.com/sponsors/runningcode)
+Thank you Doist for your sponsorship!
+
+<img width=350" alt="Doist" src="https://cms.qz.com/wp-content/uploads/2020/11/doist-logo-standard-512.png">
+
+[Sponsor Fladle!](https://github.com/sponsors/runningcode)
 
 ## Trusted by
 
 The following companies test their Android app using Fladle.
 
-<img width="256" alt="SoundCloud" src="https://upload.wikimedia.org/wikipedia/de/thumb/f/f4/SoundCloud_-_Logo.svg/200px-SoundCloud_-_Logo.svg.png"> <img width="256" alt="Zalando" src="https://www.paypalobjects.com/digitalassets/c/gifts/media/catalog/product/z/a/zalando_product_1.png"> <img width="256" alt="Robinhood" src="https://www.nachgefragt.net/wp-content/uploads/2018/10/neues-logo-robinhood.png">
+<img width="256" alt="SoundCloud" src="https://upload.wikimedia.org/wikipedia/de/thumb/f/f4/SoundCloud_-_Logo.svg/200px-SoundCloud_-_Logo.svg.png"> <img width="256" alt="Zalando" src="https://www.paypalobjects.com/digitalassets/c/gifts/media/catalog/product/z/a/zalando_product_1.png"> <img width="256" alt="Robinhood" src="https://logos-world.net/wp-content/uploads/2021/03/Robinhood-Symbol.png">
 <img width="256" alt="Yelp" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/ad/Yelp_Logo.svg/640px-Yelp_Logo.svg.png"> <img width="256" alt="Salesforce" src="https://upload.wikimedia.org/wikipedia/de/thumb/f/f9/Salesforce.com_logo.svg/640px-Salesforce.com_logo.svg.png"> <img width="256" alt="Dropbox" src="https://aem.dropbox.com/cms/content/dam/dropbox/www/en-us/branding/[email protected]">
-<img width="256" alt="ImmoScout24" src="https://www.scout24.com/media/scout24/user_upload/ImmoScout24_Logo_w3000px.png"> <img width="256" alt="GrubHub" src="https://mma.prnewswire.com/media/887026/GrubHub4_Logo.jpg?p=publish&w=200">
+<img width="256" alt="ImmoScout24" src="https://upload.wikimedia.org/wikipedia/commons/f/fa/Scout24_Logo_2020.svg"> <img width="256" alt="GrubHub" src="https://mma.prnewswire.com/media/887026/GrubHub4_Logo.jpg?p=publish&w=200">
 
 
 Want to appear here? [File an issue](https://github.com/runningcode/fladle/issues/new) or [open a PR](https://github.com/runningcode/fladle/edit/master/docs/index.md)