Pass arbitrary params to Scene.load

[gerritholl]

Allow to configure arbitrary extra parameters to be passed to Scene.load.

• [x] Closes #153
• [x] Tests added
• [x] Tests passed
• [x] Passes flake8 trollflow2
• [x] Fully documented

[codecov[bot]]

Codecov Report

Merging #154 (7623ae3) into main (3ae8805) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #154      +/-   ##
==========================================
+ Coverage   95.57%   95.58%   +0.01%     
==========================================
  Files          11       11              
  Lines        2417     2425       +8     
==========================================
+ Hits         2310     2318       +8     
  Misses        107      107              

Flag	Coverage Δ
unittests	95.58% <100.00%> (+0.01%)	:arrow_up:

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Impacted Files	Coverage Δ
trollflow2/plugins/__init__.py	92.89% <100.00%> (+0.01%)	:arrow_up:
trollflow2/tests/test_trollflow2.py	99.50% <100.00%> (+<0.01%)	:arrow_up: