table plotted from a dataframe does not use custom indices but replaces row headers with integer indices.

#### Is your feature request related to a problem? Please describe.
I expected to have a simple way to customize row headers in a table.

#### Describe the solution you'd like
I would prefer row index values (which could be strings or dates) to be rendered as row headers.

#### Describe alternatives you've considered
I've used panel module table as a workaround.

#### Additional context
Add any other context or screenshots about the feature request here.

I have set up a test project here (https://github.com/guziy/hvplot-table-issue) to generate two html tables using the two ways and compare. Below are the screenshots:

* `hvplot`

* `panel.pane.DataFrame`

Reproduce the two HTML tables from the linked hvplot-table-issue test project, comparing hvplot with panel.pane.DataFrame. Trace the dataframe table entry point and determine where the custom string or date index is replaced by integer row headers. Done means hvplot renders the dataframe index as the table's row headers, matching the requested behavior.

Written by the indexing model from the issue text.