Add support for footnote-based CSL citations

[subhramit]

Currently, using footnote-based citations with CSL styles causes unexpected behavior.
Especially, while using numeric styles, the number order gets messed up.

Describe the solution you'd like
Support for CSL style footnote citations should be provided in JabRef's libreoffice integration. The working code already exists for JStyles (although written in a convoluted manner) - we have to adapt/extend it for CSL Styles (and possibly in future - for BST styles, if we add support for it).

The explanation for the cause of the problem and a high-level description of how it's solved for JStyles is available at https://devdocs.jabref.org/code-howtos/openoffice/order-of-appearance.html.

Additional context

1. One can also refer to how Zotero's LibreOffice integration solves it.
2. It would be better if we are able to have a unified backend for functionalities common for all styles - but that may be filed as a separate issue, which is not user-facing.