feat(ui): allow to get the highlight namespace

runtime/lua/vim/_meta/api.lua

@@ -1258,6 +1258,16 @@ function vim.api.nvim_get_hl_by_name(name, rgb) end
 --- @return integer
 function vim.api.nvim_get_hl_id_by_name(name) end
 
+--- Gets the active highlight namespace.
+---
+--- @param opts vim.api.keyset.get_ns Optional parameters
+---             • winid: (number) `window-ID` for retrieving a window's
+---               highlight namespace. A value of -1 is returned when
+---               `nvim_win_set_hl_ns()` has not been called for the window
+---               (or was called with a namespace of -1).
+--- @return integer
+function vim.api.nvim_get_hl_ns(opts) end
+
 --- Gets a list of global (non-buffer-local) `mapping` definitions.
 ---
 --- @param mode string Mode short-name ("n", "i", "v", ...)

runtime/lua/vim/_meta/api_keysets.lua

@@ -136,6 +136,9 @@ error('Cannot require a meta file')
 --- @field link? boolean
 --- @field create? boolean
 
+--- @class vim.api.keyset.get_ns
+--- @field winid? integer
+
 --- @class vim.api.keyset.highlight
 --- @field bold? boolean
 --- @field standout? boolean