(nvim) revert back to efm language server

[petertriho]

null-ls is being deprecated Revert back to efm + https://github.com/lukas-reineke/lsp-format.nvim

Add sort-package-json tool

Might be worth considering:

• https://github.com/mfussenegger/nvim-lint
• https://github.com/lukas-reineke/lsp-format.nvim