New in pre-release: move tabs left / right with Ctrl + Shift + PageUp / PageDown

[kjk]

You can now move tabs with a keyboard like in Chrome.

Use Ctrl + Shift + PageUp to move current tab right.

Use Ctrl + Shift + PageDown to move current tab left.

This is in addition to existing Ctrl + PageUp and Ctrl + PageDown for selecting next / previous tab.

This is implemented as CmdMoveTabLeft and CmdMoveTabRight commands so you can assign custom keyboard shortcuts for them or invoke from Ctrl + K command palette.

Requested in #4201

Available in latest pre-release build.