Add action to create docker image for ecflow

[marcosbento]

Description

As per PR title.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌦️ >> Documentation << 🌦️
https://sites.ecmwf.int/docs/dev-section/ecflow/pull-requests/PR-345

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.88%. Comparing base (3348fe7) to head (b314916).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #345   +/-   ##
========================================
  Coverage    50.88%   50.88%           
========================================
  Files         1239     1239           
  Lines        99248    99248           
  Branches     14958    14958           
========================================
+ Hits         50499    50502    +3     
+ Misses       48749    48746    -3     

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