Merge adjacent epoch flags into a single annotation

[scott-huberty]

Closes #75

Now, instead of having several 1-second annotaitons + < 1 -second gap annotations:

You have this 1-single annotation:

Leading to a much better UX.

This also removes the need for the flag_gap boilerplate, which I think really was an idiosyncrasy of the MATLAB pipeline, which couldn't leverage a native annotation structure. instead of filling small (less than 1-second) "gap" annotations between two annotation of the same description, we can just merge those annotations into a single annotation.

[codecov]

Codecov Report

Merging #151 (6d051ce) into main (a7842b2) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #151      +/-   ##
==========================================
- Coverage   78.73%   78.70%   -0.03%     
==========================================
  Files          21       21              
  Lines        1152     1141      -11     
==========================================
- Hits          907      898       -9     
+ Misses        245      243       -2     

Files	Coverage Δ
pylossless/pipeline.py	74.13% <100.00%> (-0.21%)	⬇️

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