Add mamba-org/devcontainer-features to the index (devcontainers#118)

Author: eitsupi

_data/collection-index.yml

@@ -213,3 +213,8 @@
   contact: https://github.com/withfig/features/issues
   repository: https://github.com/withfig/features
   ociReference: ghcr.io/withfig/features
+- name: Mamba Features
+  maintainer: mamba-org
+  contact: https://github.com/mamba-org/devcontainer-features/issues
+  repository: https://github.com/mamba-org/devcontainer-features
+  ociReference: ghcr.io/mamba-org/devcontainer-features