* docs - add some info on plugin option source precedence
##### SUMMARY
Add some clarity on precedence, especially from sources of the same type.
##### ISSUE TYPE
- Docs Pull Request
+label: docsite_pr
* update RST formatting
* Update docs/docsite/rst/dev_guide/developing_plugins.rst
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Co-authored-by: Aine Riordan <44700011+ariordan-redhat@users.noreply.github.com>
Co-authored-by: Aine Riordan <44700011+ariordan-redhat@users.noreply.github.com>