[Feature] EMG report

[danibene]

Description

This PR aims to generate an interactive HTML report describing EMG processing as described in #665

Proposed Changes

1. I changed the emg_plot() function so that it optionally generates an interactive plot with plotly
2. I added an emg_methods() function
3. I changed the emg_process() function so that it optionally generates a report
4. I wrote a test for generating a report
5. I modified the docstring in report.py to reference EMG; however, I did not add any EMG-specific logic for generating a summary table. I wonder if we should use bio_analyze() to generate the table rather than checking the column names within report.py

Checklist

• I have read the CONTRIBUTING file.
• My PR is targeted at the dev branch (and not towards the master branch).

[danibene]

I think the test for emg_plot is currently failing because I returned a figure even when it is generated with matplotlib to keep the option of generating a report with matplotlib instead of plotly

[codecov-commenter]

Codecov Report

Patch coverage: 86.20% and project coverage change: +1.35 🎉

Comparison is base (5116fb4) 53.88% compared to head (75c931f) 55.23%.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #841      +/-   ##
==========================================
+ Coverage   53.88%   55.23%   +1.35%     
==========================================
  Files         295      296       +1     
  Lines       13811    13905      +94     
==========================================
+ Hits         7442     7681     +239     
+ Misses       6369     6224     -145     

Impacted Files	Coverage Δ
neurokit2/misc/report.py	94.18% <ø> (+2.32%)	⬆️
neurokit2/ppg/ppg_clean.py	70.58% <33.33%> (ø)
neurokit2/ppg/ppg_methods.py	85.29% <66.66%> (ø)
neurokit2/emg/emg_clean.py	83.33% <75.00%> (+1.51%)	⬆️
neurokit2/emg/emg_methods.py	90.00% <90.00%> (ø)
neurokit2/emg/emg_plot.py	93.33% <90.24%> (-4.45%)	⬇️
neurokit2/emg/emg_process.py	95.65% <90.90%> (-4.35%)	⬇️
neurokit2/ppg/ppg_process.py	95.83% <100.00%> (ø)
neurokit2/rsp/rsp_methods.py	86.79% <100.00%> (ø)

... and 8 files with indirect coverage changes

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[DominiqueMakowski]

can we merge that?