docs(nvim): add vim-plug example

[qvalentin]

Warning: This will show errors in it current state.

[eshepelyuk]

I suggest vim-helm should be deprecated/discouraged for NeoVim users in this PR.
Since it's bringing issues when using without lazy.nvim.

[qvalentin]

@eshepelyuk what is your pov about syntax highlighting? Should helm-ls.nvim also provide basic syntax highlighting without tree-sitter?
This is currently the only thing that vim-helm has, but helm-ls.nvim has not.

[eshepelyuk]

@eshepelyuk what is your pov about syntax highlighting? Should helm-ls.nvim also provide basic syntax highlighting without tree-sitter? This is currently the only thing that vim-helm has, but helm-ls.nvim has not.

IMO existing treesitter syntax support is great and shouldn't be duplicated by this plugin.