[Docutils-develop] Substitute image options/path

[Urban A. A. <urb...@gm...>]

Is there an option to substitute image options/path in reStructuredText?

Something like:
```
.. image:: |picdir|/someImage.jpg
   :alt: SomeImage
   :width: |imagewidth|
   :target: |picdir|/someImage.jpg


.. |picdir| replace:: ./pic
.. |imagewidth| replace:: 500px
```