ci(github): add workflow to push image to Dockerhub

[RonanMorgan]

II have created a test env which will be launched every night so it would be good to update our image in dockerhub regularly

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.34%. Comparing base (767be30) to head (2c4e136). Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #320      +/-   ##
==========================================
- Coverage   94.54%   94.34%   -0.21%     
==========================================
  Files          63       66       +3     
  Lines        1594     1679      +85     
==========================================
+ Hits         1507     1584      +77     
- Misses         87       95       +8     

Flag	Coverage Δ
client	90.58% <ø> (?)
unittests	94.54% <ø> (ø)

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[frgfm]

Oops, I just remember we already had this! The workflow trigger was not changed properly recently, but I pushed a fix a few hours ago #360

Images are now pushed again to the hub so I think we can close this PR :) Feel free to reopen if I missed something!