Feature Request: control vline width so no gaps/overlap between candles

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Hello @DanielGoldfarb,

**Is your feature request related to a problem? Please describe.**
I like the _vlines_ but they sometimes overlap when ```linewidths >= 8``` or create gaps when ```linewidths < 8```. It's noticeable when the number of bars are plotted.

**Describe the solution you'd like**
* Either another argument to passed into _vlines_ so that there are no gaps or overlaps created.
* Or maybe something similar to _vlines_ that is more specific for this purpose as this feature is slightly different than the original purpose of _vlines_.

**Describe alternatives you've considered**
I have not checked if it works in **External Axes Mode**.

**Additional context**
I made a semi-dynamic Panels [Chart Class Example Notebook](https://github.com/twopirllc/pandas-ta/blob/master/examples/example.ipynb) for my **Pandas TA** Library. The _plot_ method is located at the bottom of _Input Cell 11_.

You can play around with the Chart class arguments, namely _last_ argument, in _Input Cell 12_ to see what I mean.

Here are some example chart outputs:
#### Gaps
```last = 30``` and no _linewidth_ argument used.

```last = 90``` and no _linewidth_ argument used.

```last = recent``` (recent = 251) and no _linewidth_ argument used.

```last = 2 * recent``` (recent = 502) and no _linewidth_ argument used.

```last = 30, linewidths=8```

#### Overlap
```last = 90, linewidths=8```

```last = recent, linewidths=8```

Hope this helps!

Thanks for your time,
Kevin

Start with examples/example.ipynb, especially the plot method in Input Cell 11 and the chart arguments in Input Cell 12. Reproduce the reported gaps and overlaps with different last values and linewidths, then determine a clear, tested behavior for candle spacing in both relevant plotting modes.

Written by the indexing model from the issue text.