Add temporary markdown Vim configuration

vim.nix

@@ -3,13 +3,41 @@
 {
   programs.vim = { 
     enable = true;
-    # Temporary configuration for editing Nix files
     extraConfig = ''
+    " Temporary configuration for editing Nix files
     syntax on
     set autoindent
     set expandtab
     set tabstop=2
     set shiftwidth=2
+
+    " Temporary configuration for editing markdown
+    " full configuration with plugins is described here
+    " https://blog.elnu.com/2022/06/how-to-configure-vim-for-writing
+
+    setlocal linebreak
+
+    set spell spelllang=en
+    set spelllang+=cjk " prevent CJK characters from being spellchecked
+
+    function! Characters()
+            return strchars(join(getline(1, '$'), "\n"))
+    endfunction
+function! Words()
+            return wordcount().words
+    endfunction
+
+    function! Minutes()
+            let wpm = 200
+            return (Words() + wpm / 2) / wpm
+    endfunction
+
+    set laststatus=2 " enable status line
+    set statusline+=%=%{Words()}\ words,
+    set statusline+=\ %{Characters()}\ characters,\ about
+    set statusline+=\ %{Minutes()}\ minutes
+    " remove ugly white background
+    hi StatusLine ctermfg=0 ctermbg=none cterm=bold " 0 for the terminal color 0
     '';
   };