MultiCursor

Nobody has claimed this yet.

Daniel, thank you for excellent project.
My question is this:
There is a feature in matplotlib which provides a vertical (default) and/or horizontal line cursor shared between multiple axes.
Is it possible to have something like that in mplfinance?

This is the sample code they provided with their help screen:
```python
from matplotlib.widgets import MultiCursor
import matplotlib.pyplot as plt
import numpy as np

fig, (ax1, ax2) = plt.subplots(nrows=2, sharex=True)
t = np.arange(0.0, 2.0, 0.01)
ax1.plot(t, np.sin(2*np.pi*t))
ax2.plot(t, np.sin(4*np.pi*t))

multi = MultiCursor(fig.canvas, (ax1, ax2), color='r', lw=1,
horizOn=False, vertOn=True)
plt.show()
```

Start by reviewing the matplotlib.widgets.MultiCursor example included in the issue and how mplfinance creates multiple axes. Define how a shared vertical or horizontal cursor should behave across those axes, then verify the result with a multi-panel chart similar to the provided sample.

Written by the indexing model from the issue text.