gadgets/ci/sched_cls_drop: add missing gadget.yaml

Although the gadget.yaml metadata file is not mandatory, it is best
practice to have one. This patch adds it. It will make it easier for the
next PRs.

Signed-off-by: Alban Crequy <albancrequy@linux.microsoft.com>

gadgets/ci/sched_cls_drop/gadget.yaml

@@ -0,0 +1,10 @@
+name: sched_cls_drop
+description: gadget used by the CI
+homepageURL: https://inspektor-gadget.io/
+documentationURL: https://inspektor-gadget.io/docs/latest/
+sourceURL: https://github.com/inspektor-gadget/inspektor-gadget
+gadgetParams:
+  iface:
+    key: iface
+    defaultValue: ""
+    description: Network interface to attach to