Modify workflow to build at midnight as well as pushes

[howard]

Purpose

In case dependencies break, or there is incompatibility with new minor releases of a PHP version in periods where libflexport is updated infrequently, the library could break without anyone knowing, because there are no periodic builds.

Approach

In addition to pushes, build daily at midnight.

Open Questions and Pre-Merge TODOs

• composer lint and composer fix was executed. workflow change.
• Tests were written and pass with 100% coverage.
• A issue with a detailed explanation of the problem/enhancement was created and linked. overkill.

[codecov-io]

Codecov Report

Merging #120 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             develop   #120   +/-   ##
========================================
  Coverage        100%   100%           
  Complexity       269    269           
========================================
  Files             49     49           
  Lines            700    700           
========================================
  Hits             700    700

Flag	Coverage Δ	Complexity Δ
#unittests	100% <ø> (ø)	269 <ø> (ø)	⬇️

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