Adding floating window support

[Freyskeyd]

This PR aims to add the floating window support for terminal actions (like RustDebuggables, RustRunnables and so on).

The floating window can be configured:

local config = {
  ...
  window = {
    width = 0.9, -- width ratio
    height = 0.9, -- height ratio
    max_width = 200, -- max width of the terminal window
    max_height = 60, -- max height of the terminal window
    border = "single", -- Border style for the terminal window (see `:h nvim_open_win`)
    floating = false, -- Define if the terminal window should be floating or not (disabled by default)
  }
}

Feel free to suggest modifications :)

Signed-off-by: Freyskeyd [email protected]

[simrat39]

Looks good, although wondering why not add an executor for something like toggleterm?

[Freyskeyd]

I just wanted to keep the dependencies free of another component that can be more heavy than just a little configuration :)

But I can update the PR if needed.