Improve Select type cell editor

[budnix]

Context

The PR improves the select-type cell editor. Changes concern:

• Add support for Tab keys. There is the possibility to select the next/previous cell by hitting the navigation keyboard shortcuts while the editor is opened;

Things that already worked but are not described in Docs:

• There is native support for keyboard shortcuts for opening the native dropdown list.
  • Shift+ArrowDown/ArrowUp on macOS;
  • Alt+ArrowDown/ArrowUp on Windows;

How has this been tested?

I tested the changes locally and I covered the feature with new tests.

Types of changes

• New feature or improvement (non-breaking change which adds functionality)

Related issue(s):

1. fixes https://github.com/handsontable/dev-handsontable/issues/609

Affected project(s):

• handsontable

Checklist:

• I have reviewed the guidelines about Contributing to Handsontable and I confirm that my code follows the code style of this project.
• I have signed the Contributor License Agreement
• My change requires a change to the documentation.