Adding nvim-cmp plugin (#25)

* started adding nvim-cmp

* nvim-cmp: added snippet option

* nvim-cmp: added mapping option

* nvim-cmp: added completion option

* nvim-cmp: added confirmation config option

* nvim-cmp: added formatting options

* nvim-cmp: added matching option

* nvim-cmp: added sorting option

* nvim-cmp: added sources option

* nvim-cmp: added a bunch of sources

* nvim-cmp: auto enabling cmp source plugins should mostly work now

* nvim-cmp: added view option

* nvim_cmp: added window option

* nvim-cmp: added experimental option

* nvim-cmp: mappingPresets now works

plugins/completion/nvim-cmp/cmp-helpers.nix

@@ -0,0 +1,54 @@
+{ lib, pkgs, ... }@attrs:
+let
+  helpers = import ../../helpers.nix { lib = lib; };
+in with helpers; with lib;
+{
+  mkCmpSourcePlugin = { name, extraPlugins ? [], useDefaultPackage ? true, ... }: mkPlugin attrs {
+    inherit name;
+    extraPlugins = extraPlugins ++ (lists.optional useDefaultPackage pkgs.vimPlugins.${name});
+    description = "Enable ${name}";
+  };
+
+  pluginAndSourceNames = {
+    "luasnip" = "cmp_luasnip";
+    "snippy" = "cmp-snippy";
+    "ultisnips" = "cmp-nvim-ultisnips";
+    "vsnip" = "cmp-vsnip";
+    "buffer" = "cmp-buffer";
+    "calc" = "cmp-calc";
+    "dictionary" = "cmp-dictionary";
+    "digraphs" = "cmp-digraphs";
+    "omni" = "cmp-omni";
+    "spell" = "cmp-spell";
+    "nvim_lsp" = "cmp-nvim-lsp";
+    "nvim_lsp_document_symbol" = "cmp-nvim-lsp-document-symbol";
+    "nvim_lsp_signature_help" = "cmp-nvim-lsp-signature-help";
+    "vim_lsp" = "cmp-vim-lsp";
+    "path" = "cmp-path";
+    "git" = "cmp-git";
+    "conventionalcommits" = "cmp-conventionalcommits";
+    "cmdline" = "cmp-cmdline";
+    "cmp-cmdline-history" = "cmp-cmdline-history";
+    "fuzzy_buffer" = "cmp-fuzzy-buffer";
+    "fuzzy_path" = "cmp-fuzzy-path";
+    "rg" = "cmp-rg";
+    "fish" = "cmp-fish";
+    "tmux" = "cmp-tmux";
+    "zsh" = "cmp-zsh";
+    "crates" = "crates-nvim";
+    "npm" = "cmp-npm";
+    "cmp-clippy" = "cmp-clippy";
+    "cmp_tabnine" = "cmp-tabnine";
+    "copilot" = "cmp-copilot";
+    "dap" = "cmp-dap";
+    "emoji" = "cmp-emoji";
+    "greek" = "cmp-greek";
+    "latex_symbols" = "cmp-latex-symbols";
+    "look" = "cmp-look";
+    "nvim_lua" = "cmp-nvim-lua";
+    "pandoc_references" = "cmp-pandoc-references";
+    "cmp_pandoc" = "cmp-pandoc-nvim";
+    "treesitter" = "cmp-treesitter";
+    "vimwiki-tags" = "cmp-vimwiki-tags";
+  };
+}