Allow colorscheme override

[Red-M]

I like this theme a lot but I'd like to provide a function similar to the palette and theme overrides but for when the colorscheme is defined.

An example would be:

cs = vim.tbl_deep_extend("force", cs, Config.overrideColorscheme and Config.overrideColorscheme(cs, p, config, hp) or {})

at this line which would allow changing colour values for all of the other pre-computed colours provided by the palette. Please do note that this example does not work as cs is a local to the file and has some builtin lua functions applied to it that I don't yet understand, however this functionality would be really good for people who wish to slightly tweak the existing themes and filters to create, effectively, mini-forks of the existing ones without having to do a lot of work to offer them back (as not everyone else may like them).

Previously I had a copy of this repository as just files, in my dotfiles repository as a hackish workaround (I've moved since to a fork) and modifying them directly but doing this would make things a lot easier for myself and potentially for others who would enjoy tweaking a few things or making divergent themes based on monokai.

[loctvl842]

Thanks for liking this theme and your comment. I'll consider to support for that feature. Thanks a lot.