- use the Basealt LLC logo for About system

See https://bugzilla.altlinux.org/39847

- update year for copyright to 2023
- set codename to Mendelevium

- import contents of indexhtml from Alexey Osotov

- add /usr/share/install3/lightdm-gtk-greeter.conf
  to change the keyboard layout in greeter
- remove wrong web links

Removed at the request of Marija Belyaeva <mvb@basealt.ru>

like in branding-alt-workstation

- add /etc/altlinux-release to package (fixed ALT#41741).
- update Provides.

- Lighten the background of list boxes (closes: 41514).
- Fix: Don't specify extra horizontal margins for inputs in
  alterator-listbox tables.
- Fix: Don't restrict the width of the top panel buttons.

To the pity, it seems there is currently no way to alter the color
that is used to highlight the currently selected option:

* https://stackoverflow.com/questions/17698110/how-to-change-color-of-selection-in-select-option

* https://stackoverflow.com/questions/26392014/change-color-of-selected-option-in-html-select-input

The horizontal paddings of a table cell and of the input inside it
aren't combined properly resulting in inputs that are wider than the
surrounding cell.

Some buttons should be wider in accordance with their text.

- year auto-substitution in (c)

- release up

- colors changed

- images and bootsplash fixed

Don't preserve previously installed /etc/altlinux-release:
we are keep BUILD_ID in /etc/os-release now, it is enough.

And require alt-os-release filetrigger.

- images and bootsplash changed

- version bump
- 'Next' button size fixed