docs: add new example for multi-destination exporting to Sphinx Doc (#5087)

* add new example for multi-destination exporting

* update comments

* better comments

* update ending & links

* add link to the collector spec

* ruff formatting

* Apply suggestions from code review

Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>

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Co-authored-by: Mike Goldsmith <goldsmith.mike@gmail.com>
Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>