time series forecasting model
# What does this PR do?

This PR implements a vanilla encoder-decoder Transformer for time-series forecasting.

_The documentation is not available anymore as the PR was closed or merged._<|||||>cc'ing @mishig25 here - there seems to be an issue with the docs being built. The model is added to the toctree, but it's saying:

```
Traceback (most recent call last):
  File "/usr/local/bin/doc-builder", line 8, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.8/site-packages/doc_builder/commands/doc_builder_cli.py", line 47, in main
    args.func(args)
  File "/usr/local/lib/python3.8/site-packages/doc_builder/commands/build.py", line 96, in build_command
    build_doc(
  File "/usr/local/lib/python3.8/site-packages/doc_builder/build_doc.py", line 427, in build_doc
    sphinx_refs = check_toc_integrity(doc_folder, output_dir)
  File "/usr/local/lib/python3.8/site-packages/doc_builder/build_doc.py", line 482, in check_toc_integrity
    raise RuntimeError(
RuntimeError: The following files are not present in the table of contents:
- model_doc/time_series_transformer
Add them to ../transformers/docs/source/en/_toctree.yml.
```<|||||>Mishig the failure on the doc was due to a typo (comment is hidden now since the suggestion was accepted) nothing to do for you :-)