Add Neovim cmp autocompletion

Finally a fast none disturbing auto completion.
lsp_signature_nvim is kept as it provides info while filling in
arguments.
cmp lsp didn't work in my case, so didn't add it.

home/programs/neovim.nix

@@ -185,7 +185,6 @@ in {
 
   # - https://github.com/glacambre/firenvim Give it another try, integrates neovim into firefox
   # - https://github.com/lambdalisue/vim-pager/ (try once I use neovim as pager again)
-  # - https://github.com/hrsh7th/nvim-cmp (due to actual help of each parameter while adding values to function call)
 
   # - https://github.com/weilbith/nvim-code-action-menu/ Check again in future, right now not of much useness on my setup.
   #
@@ -309,6 +308,15 @@ in {
       '';
     }
 
+    {
+      plugin = nvim-cmp;
+      type = "lua";
+      config = pkgs.lib.fileContents ./neovim/plugins/cmp.lua;
+    }
+    cmp-omni
+    cmp-buffer
+    cmp-nvim-lua
+
     {
       plugin = lsp_signature-nvim;
       type = "lua";

home/programs/neovim/plugins/cmp.lua

@@ -0,0 +1,16 @@
+require('cmp').setup({
+    view = {
+        entries = 'native',
+    },
+
+    experimental = {
+        ghost_text = true,
+    },
+
+    sources = require('cmp').config.sources({
+        { name = 'omni' },
+        { name = 'nvim_lua' },
+    }, {
+        { name = 'buffer' },
+    }),
+})