Lightweight-charts

Enhancements
- Added the `header` attribute to `Table`, which operates identically to `footer`.
- Added the `return_clicked_cells` parameter to `create_table`, which will return the heading name of the clicked cell within a callback.
- Added more style parameters to `Table`.
- Added the `text` parameter to `legend`, allowing for static text to be displayed alongside the crosshair data.


Bug Fixes
- Fixed PyQt5 attemping to use contextMenuPolicy.

Bug Fixes:
- Screen now defaults to the active screen rather than the `0` screen.
- `null` values given in chart data are now removed and replaced with whitespace.
- Closing the chart window now cleanly exits.
- Fixed a bug causing the `offset` parameter to be greater than `0` when there is no offset.

Enhancements:
- Hotkeys can now use any character, and modifier keys are not required.
- Refactored the colors of the topbar, searchbox, toolbox, and widgets for consistency.
- Toolbox/interval refactoring and simplification.
- Histograms now show up in the legend, and will use shorthand notation by default (e.g 34k rather than 34000).

Enhancements:

- added the `align` parameter to all topbar widgets, allowing for individual widgets to be placed either on the left or right hand side of the topbar.
- DIsabled QtChart’s context menu by default.

Bug Fixes:
- The `screenshot` method now works for subcharts.
- Tables will still render if a `NoneType` is passed to them as a value.
- Qt and Wx charts no longer throw an error when using the toolbox.

Enhancements:
- added the `create_histogram` method and the `Histogram` object.
- added the `round` parameter to `trend_line` and `ray_line`
- chart.set can now be given line data.


Bug Fixes:
- `NaN` values can now be given when setting data, and will leave a blank space in the data.
- `resize` will now change the chart wrapper’s size as well as the chart itself.

Enhancements:
- The `start_date` parameter of `vertical_span` can take a list or tuple of dates to create multiple vertical lines. 84
- Added style parameters to drawings. 99

Bug Fixes:
- `VerticalSpan.delete()` now works as intended.
- Drawings no longer show up in the legend. 101
- Fixed pandas API types error (thanks jamesbaber1!)