Docker layer caching

[shimwell]

Proposed changes

Reduces the docker publish time by 1 min using docker layer caching

caching can be seeing in the gh action
https://github.com/fusion-energy/paramak/runs/4217202863?check_suite_focus=true

Followed this tutorial
https://evilmartians.com/chronicles/build-images-on-github-actions-with-docker-layer-caching

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

[codecov]

Codecov Report

Merging #129 (7a661f0) into develop (67bade1) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #129   +/-   ##
========================================
  Coverage    97.73%   97.73%           
========================================
  Files           76       76           
  Lines         4689     4689           
========================================
  Hits          4583     4583           
  Misses         106      106           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 67bade1...7a661f0. Read the comment docs.