Too high startuptime

[brianhuster]

Today CopilotChat.nvim has too hight startuptime (80ms).

I think I will send a pull request that refactor it a bit to lower startuptime. In the main file (init.lua), I will make it not require any other module at script level (but only in function level). This is to avoid unnecessarily loading all modules at startuptime. What do you think?

[jellydn]

Actually, you could use lazy.nvim to load the plugin on command so the start-up won't be an big issue.

What do you think? @deathbeam

[brianhuster]

I know that, but I just don't like the way Lua plugins often have much higher startuptime than legacy Vimscript plugins just because they often try to load the whole plugin on startup, which is just unnecessary. Also among many active plugin managers for Neovim, lazy.nvim is the only one that supports such lazy-loading. Even if I lazy-load the plugin with the command CopilotChat, then a chat buffer will take a long time to open

For the PR, I will need to make some refactoring. But I would like to ask some questions first.

1. Currently it seems like the table to save config is in the main module. I would like to move it to require('CopilotChat.config').config, is that ok? The table for default config could be in require('CopilotChat.config').default, I think
2. Initializing code should live in runtimepath/plugin/CopilotChat.lua, because that is what it is made for. See Neovim document :h load-plugins

 	The result is that all directories in 'runtimepath' will be searched
	for the "plugin" sub-directory and all files ending in ".vim" or
	".lua" will be sourced (in alphabetical order per directory),
	also in subdirectories. First "*.vim" are sourced, then "*.lua" files,
	per directory.

That would also save users from having to run the function require('CopilotChat').setup() just to use plugin with default config.