More layout options like floating window

[sahilsehwag]

• It would be amazing if there could be floating window support for this plugin.
• It would be even better if the user can provide his own layout command(similar to fzf_layout), along with a way to give dimensions for the layout like width/height or both in case of floating windows
• Its more convenient if we can have an additional mapping in buffer tree to close the explorer buffer like escape or q