feat: add skip_toggle option to ignore some opened terminals when toggling

[tanloong]

This adds a skip_toggle option to allow users skip specific terminals when toggling. A use case is when using the file explorer lf.nvim which is based on toggleterm.nvim. A common scenario on my side is that there are two hidden terminals, an Lf terminal and a Shell terminal, where I hope the Shell terminal always shows up on ToggleTerm, even though it is not the last toggled one.

With the skip_toggle this behavior can be achieved:

toggleterm.setup({
    open_mapping = [[<m-=>]],
    skip_toggle = function(t)
        return t and t.cmd and vim.startswith(t.cmd, "lf ")
    end,
}

simplescreenrecorder-2024-01-03_22.21.51.mp4