sed: show an empty pattern space as $ in l, even without a newline

[DePasqualeOrg]

When the pattern space is empty and its input line had no final newline, l prints nothing, while GNU sed prints $. For example, printf a | sed -n 's/a//;l' prints nothing instead of $. This PR prints $ and a newline for an empty pattern space in every case.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.84%. Comparing base (3676eac) to head (5757f78).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #595      +/-   ##
==========================================
+ Coverage   94.82%   94.84%   +0.01%     
==========================================
  Files          14       14              
  Lines        7212     7210       -2     
  Branches      428      427       -1     
==========================================
- Hits         6839     6838       -1     
+ Misses        372      371       -1     
  Partials        1        1              

Flag	Coverage Δ
macos_latest	96.38% <100.00%> (+0.01%)	⬆️
ubuntu_latest	96.32% <100.00%> (+0.01%)	⬆️
windows_latest	0.00% <0.00%> (ø)

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[sylvestre]

Thanks for your PR