Prepare 0.2.18 release

[alejoe91]

• added release notes
• added sphinx_rtd_theme to [docs] installation
• updated README to be in "sync" with SpikeInterface

[zm711]

just a typo fix

[codecov-commenter]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (45a6782) 89.07% compared to head (e331871) 89.24%.
Report is 5 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #227      +/-   ##
==========================================
+ Coverage   89.07%   89.24%   +0.17%     
==========================================
  Files          10       10              
  Lines        1711     1702       -9     
==========================================
- Hits         1524     1519       -5     
+ Misses        187      183       -4     

Files	Coverage Δ
src/probeinterface/generator.py	98.33% <100.00%> (+0.02%)	⬆️
src/probeinterface/io.py	88.00% <100.00%> (ø)
src/probeinterface/plotting.py	79.16% <100.00%> (+0.63%)	⬆️
src/probeinterface/probe.py	92.87% <75.00%> (-0.12%)	⬇️
src/probeinterface/probegroup.py	87.70% <60.00%> (+0.88%)	⬆️

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[alejoe91]

@samuelgarcia ready to merge and release