4.4.0

* Add "Nova" theme for Firefox 155 and later.
* Show "New Tab" button like a new tab, matching to Firefox does.
* Copy single link from single tab correctly.
* Support "Copy links in group" command in the context menu on tab groups.
* Drop-shadow to indicate scrollable state is now available in the pinned tabs area, not only in regular tabs area.
* Expand height of the pinned tabs area automatically, when at least half of the last row is visible after resizing.
* Shrink height of the pinned tabs area automatically, when empty rows are there after closing of pinned tabs.
* Better scaling of custom dialogs on hi-DPI displays.
* Show the QR code to share a tab in the sidebar if the `<all_urls>` permission is not granted.
* The root element of the sidebar panel now has a `data-style` attribute with the name of the active theme, for more customizability with user stylesheet. You'll be able to apply style rules only for specific theme with selectors like `:root[data-style="nova"]`.
* API: Introduce [`remove-tab-keeping-children`](https://github.com/piroor/treestyletab/wiki/API-for-other-addons#close-only-parent-tabs-keeping-their-children) message to close parent tabs keeping their children. ([initiallly implemented by Peuj](https://github.com/piroor/treestyletab/pull/3934), thanks!)
* Fix mistakes in `en` locale by [scrypt-kitty](https://github.com/scrypt-kitty) ([#3941](http://github.com/piroor/treestyletab/pull/3941) and [#3942](http://github.com/piroor/treestyletab/pull/3942)), Thanks!
* [Add `sk` locale by rraddatch](github.com/piroor/treestyletab/pull/3946). Thanks!