ADOPTERS.md: add Fivetran (#3409)

Signed-off-by: Felipe Neuwald <felipe.neuwald@fivetran.com>

ADOPTERS.md

@@ -7,6 +7,7 @@
 - [Container Solutions](http://container-solutions.com/)
 - [DaangnPay](https://www.daangnpay.com/)
 - [Epidemic Sound](https://www.epidemicsound.com/)
+- [Fivetran](https://www.fivetran.com)
 - [Form3](https://www.form3.tech/)
 - [GoTo](https://www.goto.com/)
 - [Heureka Group](https://heureka.group)