add batch_size limit for max # of files to publish at one (dayli) run

[nicHoch]

addresses #333

[codecov-commenter]

Codecov Report

Patch coverage: 62.50% and project coverage change: -0.02 :warning:

Comparison is base (1eeb4ee) 77.00% compared to head (bb6c822) 76.98%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #334 +/- ## ========================================== - Coverage 77.00% 76.98% -0.02% ========================================== Files 63 63 Lines 6557 6562 +5 ========================================== + Hits 5049 5052 +3 - Misses 1508 1510 +2 ``` | [Impacted Files](https://codecov.io/gh/i4Ds/STIXCore/pull/334?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=i4Ds) | Coverage Δ | | |---|---|---| | [stixcore/processing/publish.py](https://codecov.io/gh/i4Ds/STIXCore/pull/334?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=i4Ds#diff-c3RpeGNvcmUvcHJvY2Vzc2luZy9wdWJsaXNoLnB5) | `82.64% <62.50%> (-0.30%)` | :arrow_down: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=i4Ds). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=i4Ds)

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[nicHoch]

yes the publishing is called once a day via cron. And knows what was already published and therefore can "go on" next time.