New features and enhancements

• Introduce ui.button_group (#2821 by @codingpaula, @falkoschindler)
• Introduce ui.dropdown_button (#2821 by @codingpaula, @falkoschindler)
• Introduce ui.range (#1191, #2762 by @frankvp11, @codingpaula)
• Introduce ui.clipboard functions (#2575, #2594 by @ZeroCool940711, @falkoschindler)
• Add an on_multi_upload callback for ui.upload (#2698, #2765 by @rcovic, @d-meehan, @falkoschindler)
• Add SVG events to ui.interactive_image (#2745 by @frankvp11, @falkoschindler)
• Allow registering events after element instantiation (#2687, #2704, #2708 by @petergaultney, @falkoschindler)
• Make libsass optional, replacing ui.add_style with ui.add_css, ui.add_scss and ui.add_sass (#2796, #2809 by @psy0rz, @rodja, @falkoschindler)
• Let run.io_bound and run.cpu_bound maintain type signatures of their callbacks (#2733 by @petergaultney)
• Make On Air reconnect more robust (#2818 by @rodja)
• Terminate On Air connection more elegantly (#2761 by @rodja)

Bugfixes

• Fix jumping cursor for ui.editor (#2611, #2756 by @Gilser, @intrinsically, @falkoschindler)
• Fix displayed order of ui.select options (#2137 by @CrystalWindSnake, @falkoschindler)
• Update ui.number after changing its limits (#2743, #2753 by @eddie3ruff, @falkoschindler)

Documentation

• Fix instruction about how to use the autopep8 command for code contributions (#2750 by @codingpaula, @falkoschindler)