vim: add elixir plugin

lib/vim/init.vim

@@ -102,6 +102,7 @@ augroup filetypes
   autocmd bufnewfile,bufread urls,config set filetype=conf
   autocmd bufnewfile,bufread *.elm packadd elm-vim | set filetype=elm shiftwidth=4
   autocmd bufnewfile,bufread *.md packadd vim-pandoc | packadd vim-pandoc-syntax | set filetype=pandoc
+  autocmd bufnewfile,bufread *.ex,*.exs packadd vim-elixir | set filetype=elixir
   autocmd filetype haskell packadd haskell-vim | set keywordprg=hoogle\ -i
   autocmd filetype javascript packadd vim-javascript
   autocmd filetype make setlocal noexpandtab

packages/vim.nix

@@ -81,6 +81,7 @@
         dhall-vim
         elm-vim
         emmet-vim
+        vim-elixir
         haskell-vim
         niveumPackages.vimPlugins-icalendar-vim
         niveumPackages.vimPlugins-jq-vim