Show a floating popup in neovim with lua

init.lua

-- show a floating popup
local function show_popup(size_percentage, filetype, title, lines)
  -- build buffer
  local buf = vim.api.nvim_create_buf(false, true)
  vim.api.nvim_buf_set_option(buf, "bufhidden", "wipe")
  vim.api.nvim_buf_set_option(buf, "filetype", filetype)
  vim.api.nvim_buf_set_keymap(buf, "n", "<esc>", ":bd<cr>", { nowait = true, noremap = true, silent = true })
  vim.api.nvim_open_win(buf, true, {
    style = "minimal",
    relative = "editor",
    width = math.ceil(vim.o.columns * size_percentage),
    height = math.ceil(vim.o.lines * size_percentage),
    row = math.ceil(vim.o.lines * (1 - size_percentage) / 2),
    col = math.ceil(vim.o.columns * (1 - size_percentage) / 2),
    border = "double",
    title = title,
  })
  -- content
  vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
end

-- example of use:
vim.api.nvim_create_user_command("ShowPopup", function()
  show_popup(0.5, "markdown", "Hello world", { "hello", "world" })
end, {})