Update vim.validate usages to avoid deprecated warning

[fernandoalexandre]

Fixed :checkhealth warning (mentioned also in #59 ):
vim.validate is deprecated. Feature will be removed in Nvim 1.0

ADVICE:
    use vim.validate(name, value, validator, optional_or_msg)

instead.
stack traceback:
/home/user/.local/share/nvim/lazy/auto-dark-mode.nvim/lua/auto-dark-mode/init.lua:22
/home/user/.local/share/nvim/lazy/auto-dark-mode.nvim/lua/auto-dark-mode/init.lua:163
/home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/core/loader.lua:387

[f-person]

thank u!<3

[nekowinston]

Ah, I didn't react to this in time, sorry.
This PR breaks the plugin for neovim 0.10 and older; and we're quite a way from Neovim 1.0.
The tests on main are currently failing, I forgot to have them run on PR branches. @f-person

[fernandoalexandre]

Ah, I didn't react to this in time, sorry. This PR breaks the plugin for neovim 0.10 and older; and we're quite a way from Neovim 1.0. The tests on main are currently failing, I forgot to have them run on PR branches. @f-person

@f-person @nekowinston Apologies for this impact I'm actually looking into a new PR to make this logic a version-based, apply if it's 0.11 or over, and use the old logic otherwise.

Edit: Created #61