Support cticks

[ahuang11]

I tried very long time to get the matplotlib test to work, but couldn't :/

If I set hv.extension("matplotlib"), this works; but without that extension, it doesn't detect cbar weirdly.

import pandas as pd
import holoviews as hv
import hvplot.xarray
import numpy as np
import xarray as xr

backend = "matplotlib"
da2 = xr.DataArray(
    data=np.arange(27).reshape((3, 3, 3)),
    coords={"y": [0, 1, 2], "x": [0, 1, 2]},
    dims=["y", "x", "other"],
    name="test2",
)

plot = da2.isel(other=2).hvplot(cticks=[5, 10])
handles = hv.renderer(backend).get_plot(plot).handles
if backend == 'matplotlib':
    print(handles)
    assert handles["cbar"].get_ticks().tolist() == [5, 10]

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 88.44%. Comparing base (6c96c7e) to head (a145f55).
Report is 8 commits behind head on main.

Files	Patch %	Lines
hvplot/converter.py	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1368      +/-   ##
==========================================
+ Coverage   87.39%   88.44%   +1.04%     
==========================================
  Files          50       50              
  Lines        7490     7389     -101     
==========================================
- Hits         6546     6535      -11     
+ Misses        944      854      -90     

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[maximlt]

Minor update, reflecting the changes made to the Customization guide to the converter docstring.