refactor: Refactor deprecated functions

[eric-huang-git]

• Replaced nvim_buf_set_option and nvim_win_set_option -> nvim_set_option_value
• Replaced vim.api.nvim_exec([[pwd]], true) -> vim.fn.getcwd()
• Replaced vim.api.nvim_get_option -> vim.api.nvim_get_option_value
• Used newer syntax on vim.validate
• Commented out unused/unreachable code
• Ran stylua .

---

I tried to use extmark for highlights, but couldn't quite get it working
This branch seems to work on my computer, please do let me know if this needs to run more tests.
(P.S. I don't fully understand the gendocs.lua, so maybe I need some instructions on how to make the docs)

[johnDeSilencio]

Bump. Would be nice to see the deprecation warnings go away for this awesome plugin

[max397574]

thx