[WIP] Allow components as tab labels

[chriddyp]

WIP
experiments in tabs enabled by plotly/dash-renderer#26

allows tabs to have components as labels, like:

dcc.Tabs(
    tabs=[
        {'label': 'Market Value', 'value': 1},
        {
            'label': dcc.Dropdown(
                id='my-dropdown',
                options=[
                    {'label': 'Option {}'.format(i), 'value': i}
                    for i in range(5)
                ]
            ),
            'value': 2
        },
        {'label': 'Predictions', 'value': 3},
        {'label': 'Target Pricing', 'value': 4},
    ],
    value=3,
)

would allow things like links, icons, or custom formatted tab labels.

[valentijnnieman]

@chriddyp Could you verify if this WIP PR is still needed to be open? I'm trying to clean up all the PR's.

[Marc-Andre-Rivet]

This PR seems very interesting but has been inactive for over a year. Closing. Do feel free to re-open if it becomes active again.