feat: add windows-list to allow custom window candidates

[henry-hsieh]

In multi-windows mode, there will be some windows you don't want to jump to. For example, float windows based plugins like NeoZoom.lua or detour.nvim.

A windows-list option is added to supply these scenarios. Its default value is much like the original code: all windows except unfocusable windows. It's allowing user jump between float windows, but not the windows cannot be focus to, which are used a lot by incline.nvim.

[henry-hsieh]

Another option is to move unfocusable windows back to the valid_win checks if we don't want unfoucusable windows to be moved to.

[smoka7]

Another option is to move unfocusable windows back to the valid_win checks if we don't want unfoucusable windows to be moved to

Since we have excluded_filetypes, windows_list seems a bit redundant. Filtering unfocusable windows is a good idea. I think we should do this instead.

[henry-hsieh]

The reason why I want to add this option is that detour.nvim actually create several float windows on top of themselves. They all have the same filetype, but only the top window is where I want to jump to. It's may only useful when filetype cannot distinguish jump window.

[smoka7]

Okay, it looks good to me. If you're done with it, I'm going to merge it.

[henry-hsieh]

I have finished the PR. You can merge it now. Thanks!