[Feature Request]: Add `BufferLineCloseHidden` method

[wenqian]

What?

Provide a BufferLineCloseHidden method to close hidden buffers while preserving open windows.

Here is a simple implement:

local delete_hiddent_buffer = function()
	local non_hidden_buffer = {}
	for _, win in ipairs(vim.api.nvim_list_wins()) do
		local buf = vim.api.nvim_win_get_buf(win)
		non_hidden_buffer[buf] = true
	end

	local buffers = vim.api.nvim_list_bufs()
	for _, buf in ipairs(buffers) do
		local modified = vim.fn.getbufvar(buf, "&modified")
		-- we won't delete modified buffer
		if modified ~= 1 and non_hidden_buffer[buf] == nil then
			vim.api.nvim_buf_delete(buf, {
				force = false,
			})
		end
	end
	require("bufferline.ui").refresh()
end

Why?

Currently, there is BufferLineCloseOthers, but it closes other open windows. In split-screen scenarios, I often wish to keep the open windows while closing other buffers.

[Akin]

@fioncat there are many plugins such as nvim-bufdelete and numerous others that solve the problem of closing X buffer and not messing with the window arrangement. I'm not going to add that natively here because there are already good enough solutions and frankly I'm not looking to maintain even more functionality (which will just bring all it's own issues)