Finalize README versions

Bump versions of plotlywidget and jupyterlab-plotly to 1.1.0-rc.1

Bump versions of plotlywidget and jupyterlab-plotly to 1.1.0-rc.1

Bump versions of plotlywidget and jupyterlab-plotly to 1.1.0-rc.1

Merge pull request plotly#1666 from plotly/v4_integration

Version 4 integration

Merge pull request plotly#1666 from plotly/v4_integration

Version 4 integration

Merge pull request plotly#1666 from plotly/v4_integration

Version 4 integration

Merge pull request plotly#1666 from plotly/v4_integration

Version 4 integration

Merge pull request plotly#1666 from plotly/v4_integration

Version 4 integration

Update to rc1 versions