plot_rank: add ref_line, bar, vlines and marker_vlines kwargs

[aloctavodia]

Fix #1396

• Follows official PR format
• Includes a sample plot to visually illustrate the changes (only for plot-related functions)
• New features are properly documented (with an example if appropriate)?
• Includes new or updated tests to cover the new feature
• Code style correct (follows pylint and black guidelines)
• Changes are listed in changelog

idata = az.load_arviz_data("centered_eight")
az.plot_rank(idata, var_names="mu", kind="vlines", vlines_kwargs={'lw':0}, marker_vlines_kwargs={'lw':3});

az.plot_rank(idata, var_names="mu", ref_line_kwargs={"line_width":2, "line_color":"gray"},
bar_kwargs={"width":50}, backend="bokeh");

[codecov]

Codecov Report

Merging #1419 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1419      +/-   ##
==========================================
+ Coverage   91.56%   91.59%   +0.02%     
==========================================
  Files         105      105              
  Lines       11098    11137      +39     
==========================================
+ Hits        10162    10201      +39     
  Misses        936      936              

Impacted Files	Coverage Δ
arviz/plots/rankplot.py	90.32% <ø> (ø)
arviz/plots/backends/bokeh/ppcplot.py	97.69% <100.00%> (+0.11%)	⬆️
arviz/plots/backends/bokeh/rankplot.py	94.66% <100.00%> (+1.22%)	⬆️
arviz/plots/backends/matplotlib/ppcplot.py	98.10% <100.00%> (+0.02%)	⬆️
arviz/plots/backends/matplotlib/rankplot.py	96.96% <100.00%> (+0.96%)	⬆️
arviz/plots/ppcplot.py	93.44% <100.00%> (ø)

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