Add reader for LSA-SAF data

[simonrp84]

This PR adds a reader for data produced by EUMETSAT's LSA-SAF. Right now, it only supports land surface temperature files but I plan to add additional ones soon. Tests need to be added as well, but I wanted to make a PR so gain some feedback on the way I've coded this before I do the testing for it.

• [ ] Tests added
• [ ] Fully documented

[codecov[bot]]

Codecov Report

Merging #2529 (684af00) into main (8490966) will decrease coverage by 0.20%. The diff coverage is 24.40%.

@@            Coverage Diff             @@
##             main    #2529      +/-   ##
==========================================
- Coverage   94.89%   94.69%   -0.20%     
==========================================
  Files         349      350       +1     
  Lines       50859    50986     +127     
==========================================
+ Hits        48263    48283      +20     
- Misses       2596     2703     +107     

Flag	Coverage Δ
behaviourtests	4.31% <0.00%> (-0.02%)	:arrow_down:
unittests	95.30% <24.40%> (-0.21%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
satpy/readers/lsasaf_h5.py	24.40% <24.40%> (ø)

... and 3 files with indirect coverage changes

[simonrp84]

pre-commit.ci autofix

[simonrp84]

Kinda curious that there pre-commit.ci shows failures, I ran the pre-commit checks locally before pushing!

[coveralls]

Pull Request Test Coverage Report for Build 5574764301

• 31 of 127 (24.41%) changed or added relevant lines in 1 file are covered.
• 11 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.2%) to 95.251%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
satpy/readers/lsasaf_h5.py	31	127	24.41%
<!--	Total:	31	127

Files with Coverage Reduction	New Missed Lines	%
satpy/tests/reader_tests/gms/test_gms5_vissr_l1b.py	3	98.67%
satpy/tests/reader_tests/gms/test_gms5_vissr_navigation.py	3	97.16%
satpy/tests/reader_tests/utils.py	5	84.85%
<!--	Total:	11

Totals
Change from base Build 5488743163:	-0.2%
Covered Lines:	48396
Relevant Lines:	50809

---

💛 - Coveralls