Initial ADOPTERS.MD to list organizations using OpenCost

https://github.com/opencost/opencost/issues/1831 for CNCF requirements

Signed-off-by: Matt Ray <github@mattray.dev>

ADOPTERS.MD

@@ -0,0 +1,13 @@
+# OpenCost Adopters
+
+This page contains a list of organizations who are using OpenCost in production or in stages of development.
+
+If you would like to be included in this table, please submit a PR to this file or comment to [this issue](https://github.com/opencost/opencost/issues/1831) and your information will be added.
+
+## Adopters
+
+| Organization                      | Product/Project Name                                                   | Status                   | More Information                                                     |
+| --------------------------------- | ---------------------------------------------------------------------- | ------------------------ | -------------------------------------------------------------------- |
+| Kubecost                          | Kubecost Free/Business/Enterprise                                      | Production               | <https://kubecost.com>                                               |
+
+`*` organization that is an end user of OpenCost and not a vendor/reseller