Add more options to Scrollbar (#1174)

* Make `Scrollbar` accept a table for its options

* Add `force_status`, `{expanded,shrinked}_size` options to `Scrollbar`

* Add `Scrollbar:set_forced_status`

* Add `config.force_scrollbar_status` to force `DocView` scrollbars status

data/core/config.lua

@@ -6,6 +6,8 @@ config.message_timeout = 5
 config.mouse_wheel_scroll = 50 * SCALE
 config.animate_drag_scroll = false
 config.scroll_past_end = true
+---@type "expanded" | "contracted" | false @Force the scrollbar status of the DocView
+config.force_scrollbar_status = false
 config.file_size_limit = 10
 config.ignore_files = {
   -- folders