Update collection-index.yml (devcontainers#306)

add xfrancois devcontainer-features collection

Author: xfrancois

_data/collection-index.yml

@@ -592,4 +592,9 @@
   maintainer: lnyousif
   contact: https://github.com/lnyousif/plantuml-devcontainer/issues
   repository: https://github.com/lnyousif/plantuml-devcontainer
-  ociReference: ghcr.io/lnyousif/plantuml-devcontainer
+  ociReference: ghcr.io/lnyousif/plantuml-devcontainer
+- name: Features by xfrancois
+  maintainer: xfrancois
+  contact: https://github.com/xfrancois/devcontainers-features/issues
+  repository: https://github.com/xfrancois/devcontainers-features
+  ociReference: ghcr.io/xfrancois/devcontainers-features