feat: Use extractor.nvim to extract color data

[reobin]

• Use extractor.nvim plugin instead of custom functions in .vimrc
• Migrate the whole setup to 100% nvim.
• Remove any mention of lua vs. vim colorschemes. Will bring back later when I find a way to know for sure the supported editor of a colorscheme.
• Improve how plugins are installed: use packpath directory insted of adding the plugin files in the runtimepath.
• Update nvim version in docker build.

Next steps:

• Start a new database with just the new data.
• Validate new data.
• Replace the current database with new data.
• Deploy the web app with support changes.

Closes #63