Add tectonic devcontainer feature listing (#714)

* Add tectonic devcontainer feature listing

* Fix newline at end of file in collection-index.yml

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Co-authored-by: Abdurrahmaan Iqbal <abdurriq@github.com>

Author: sjp

_data/collection-index.yml

@@ -1541,3 +1541,8 @@
   contact: https://github.com/XavierBeheydt/devcontainer-extras/issues
   repository: https://github.com/XavierBeheydt/devcontainer-extras
   ociReference: ghcr.io/xavierbeheydt/devcontainer-extras
+- name: Tectonic Feature by sjp
+  maintainer: sjp
+  contact: https://github.com/sjp/tectonic-feature/issues
+  repository: https://github.com/sjp/tectonic-feature
+  ociReference: ghcr.io/sjp/tectonic-feature