feat(config): add set_vim_background option

[cooperrunyan]

Add set_vim_background option (default true) to control whether or not vim.opt.background = '...' is included in compiler output.

There are no breaking changes here; just the ability to opt out of the plugin setting
vim.o.background.

Why?

Neovim 0.11.0 introduced the ability to auto-detect the system's color theme, updating vim.o.background accordingly. However, this only works if the user has not set vim.o.background in their configuration already.

Example

Config (using folke/lazy.nvim)

Default (Pre-existing) Behavior

options.set_vim_background = true (equivalent to the behavior before this PR).

set_vim_background_true.mov

Notice that the OptionSet autocommand doesn't run. This is because the colorscheme github_default_dark will set vim.o.background = 'dark'.

Feature

options.set_vim_background = false

set_vim_background_false.mov

Notice that now, the OptionSet autocommand does run, and the vim.o.background gets updated by Neovim.