Github actions: enabled nightly run of build and test

[neomatrix369]

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Checklist

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• [x] a clear title and description to the Pull Request has been provided
• [x] you have read
  • [x] the Contributing doc
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• [ ] ~the pull request passes the tests (`./test-coverage "tests slow-tests"``) - this will also be visible via the Code coverage report and CI/CD task on the Pull Request~
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Goal or purpose of the PR

Enabled nightly run of build and test via Github actions

Changes implemented in the PR

Added the schedule directive to the on to the end-to-end-flow workflow (github action)

[codecov[bot]]

Codecov Report

Merging #65 (dde3172) into master (bef1aa6) will not change coverage. The diff coverage is n/a.

:exclamation: Current head dde3172 differs from pull request most recent head f7ae95b. Consider uploading reports for the commit f7ae95b to get more accurate results

@@            Coverage Diff            @@
##            master       #65   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           26        26           
  Lines          498       498           
  Branches        74        74           
=========================================
  Hits           498       498           

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