added the lightning_flash_accumulation_in_vicinity cell method missing from imengluk

[maxwhitemet]

Addresses #802

Testing:

• Ran tests and they passed OK
• Added new tests for the new feature(s)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.40%. Comparing base (84a8944) to head (41b7f5c).
Report is 54 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #2064    +/-   ##
========================================
  Coverage   98.39%   98.40%            
========================================
  Files         124      134    +10     
  Lines       12212    13140   +928     
========================================
+ Hits        12016    12930   +914     
- Misses        196      210    +14     

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[lambert-p]

I have reviewed your code, it is looking good and I can't see any changes that need to be made. I will put it into second review.

[brhooper]

Thanks @maxwhitemet, these changes look as I expected them to.

I've attempted to run all of the IMPROVER tests and get failures for acceptance tests in improver_tests/acceptance/test_lightning_from_cape_and_precip.py. I think that the KGOs for these tests need updating to include the new cell method.

[brhooper]

Thanks @maxwhitemet, this all looks fine to me.

I think you'll need to pull master back into this branch before it can be merged, so that the fix to the Github actions can be included.