Make init.lua copy-paste friendly

[kdheepak]

Currently if you copy paste init.lua it gives an error because it tries to require "custom.plugins". If we want the copy paste path to be a happy path, I believe this should be commented by default.

[mech-a]

We explicitly don't want people to copy and paste init.lua in -- that installation method is for a very outdated version of kickstart.

[kdheepak]

While I generally agree that copy paste isn’t the way to do things, I do believe in this case it is a small tradeoff for getting a happy path for the copy paste use case, e.g. if I wanted to demo how easy it is to start using nvim.

Also the readme mentions that this repo is a single file configuration with examples to move to a multiple file configuration. I believe this PR will make the readme more accurate to that sentiment.

[mech-a]

Thanks for your comment - I agree that the PR brings us more in line with what we state on the readme. I think this is a good change and we won't need to adjust our installation instructions. @feoh I'm curious about your thoughts?