feat: added option to set local win opts of BufferList window and option to have cursor start on current buffer line

[truthseekeraria]

i figured adding a way to set custom local window opts of the BufferList window would be a nice way to allow for more customizability if desired, such as customizing the statuscolumn for example

as for the second thing i think it just makes more sense to have the cursor start on the line of the current buffer. even if you don't intend to move navigate through the window with the cursor, if you were to enable vim.wo.cursorline through the win_opts option for the BufferList you would get a nicer more clear visual indicator for your current buffer (which is probably what i'll use it for). i also added an option to disable it as well in case people who are used to the old behaviour don't want it to work like this (although it's probably an unnecessary option, if you think having it isn't worthwhile then i could always remove it)

also btw i think you did a pretty good job of designing this thing, it's definitely my favourite buffer navigator i've tried 👍