Fix up devcontainer config (REUSE, strict JSON, image bump) and mention it in docs

- add SPDX licensing information for REUSE compliance
- drop the JSONC comment from devcontainer.json, keeping it strict JSON
  (as required by the check-json pre-commit hook)
- bump the base image to the current ghcr.io/devture/ansible release
- mention the dev container in docs/ansible.md

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.devcontainer/Dockerfile

@@ -1,4 +1,8 @@
-FROM ghcr.io/devture/ansible:11.1.0-r0-0
+# SPDX-FileCopyrightText: 2025 Jonah Aragon
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+FROM ghcr.io/devture/ansible:11.6.0-r0-0
 
 # Install additional packages
 RUN apk add --no-cache \

.devcontainer/devcontainer.json

@@ -1,4 +1,3 @@
-// For format details, see https://aka.ms/devcontainer.json.
 {
 	"name": "matrix-docker-ansible-deploy",
 	"build": {

.devcontainer/devcontainer.json.license

@@ -0,0 +1,3 @@
+SPDX-FileCopyrightText: 2025 Jonah Aragon
+
+SPDX-License-Identifier: AGPL-3.0-or-later