Docs link python classes to docs #2633

[eldbud]

Resolves item number 2 on the original message in #2633 - link to python docs.

Added intersphinx to conf.py, also minor docs mending.

[eldbud]

@Bibo-Joshi Is there anything else i should add to this pr?

[Bibo-Joshi]

Hi. As mentioned in #2738 and offline, it would be good if you build the docs and checked for places where linking to the python/APS docs is not yet used or used wrongly. Ofc I don't expect you to check every docstring manually, that's just not feasible. However, ext/_jobqueue.py is basically the only file where we would want to link to the APS docs, so that could indeed be manually checked.
If you already did that without results, then there's nothing to add to this PR :)

[eldbud]

However, ext/_jobqueue.py is basically the only file where we would want to link to the APS docs, so that could indeed be manually checked.

If i am seeing correctly, the links to APScheduler appear in the doc of JobQueue, please see attached image.
If i am missing something there, of course i'd be happy to fix it

.

[Bibo-Joshi]

scheduler.add_job can be linked to BaseSchedule.add_job0- probably in the other methods as well :)

[eldbud]

scheduler.add_job can be linked to BaseSchedule.add_job0- probably in the other methods as well :)

done

[harshil21]

pretty much how I would do it. If there are missing/wrong references in other parts of code, we can just fix it later

[Bibo-Joshi]

Thanks for the contribution :)