Introduce MAINTAINERS.md (#662)

* Introduce MAINTAINERS.md

Signed-off-by: Tom Kerkhove <kerkhove.tom@gmail.com>

* Introduce Alumni

MAINTAINERS.md

@@ -0,0 +1,19 @@
+# Kubernetes Event-driven Autoscaling (KEDA) Maintainers
+
+## Current
+
+| Maintainer           | GitHub ID                                     | Affiliation |
+| -------------------- | --------------------------------------------- | ----------- |
+| Jeff Hollan          | [jeffhollan](https://github.com/jeffhollan)   | Microsoft   |
+| Anirudh Garg         | [anirudhgarg](https://github.com/anirudhgarg) | Microsoft   |
+| Ahmed ElSayed        | [ahmelsayed](https://github.com/ahmelsayed)   | Microsoft   |
+| Zbynek Roubalik      | [zroubalik](https://github.com/zroubalik)     | Red Hat     |
+| Tom Kerkhove         | [tomkerkhove](https://github.com/tomkerkhove) | Codit       |
+
+## Alumni
+
+| Maintainer           | GitHub ID                                     | Affiliation |
+| -------------------- | --------------------------------------------- | ----------- |
+| Aarthi Saravanakumar | [Aarthisk](https://github.com/Aarthisk)       | Microsoft   |
+| Yaron Schneider      | [yaron2](https://github.com/yaron2)           | Microsoft   |
+| Ben Browning         | [bbrowning](https://github.com/bbrowning)     | Red Hat     |