[needs triage] colorschemes added to rtp after init.lua is sourced

[mrcjkb]

Originally posted by @Rasmus-Bertell in #212

To reproduce:

• :Rocks install kanagawa.nvim
• In init.lua: vim.cmd.colorscheme("kanagawa")

Expected behaviour:

• Colorscheme loaded

Actual behaviour:

• Colorscheme not found error

Workaround:

• Install with opt=true
• require("rocks").packadd("kanagawa.nvim") before the vim.cmd.colorscheme call.

[mrcjkb]

Summary of matrix discussions:

Not sure if there's a good solution to this.
Requiring a rocks.init_rtp call would be a breaking change that is no more convenient than using rocks.packadd. Symlinking colorscheme scripts might be a bit hacky and complex.
rocks-config could help abstract this by separating init (pre-plugin-sourcing) and config scripts in some way.

[mrcjkb]

Thought: There's no harm in adding all rocks to the rtp before running the preload hooks.
This would solve the problem for rocks-config.nvim.