Toggle on WinEnter and WinLeave

Closes #39. 🎩 @brendanator and @fernandoacorreia

plugin/number_toggle.vim

@@ -1,9 +1,9 @@
 " vim-numbertoggle - Automatic toggling between 'hybrid' and absolute line numbers
 " Maintainer:        <https://jeffkreeftmeijer.com>
-" Version:           2.1.0
+" Version:           2.1.1
 
 augroup numbertoggle
   autocmd!
-  autocmd BufEnter,FocusGained,InsertLeave * if &nu | set rnu   | endif
-  autocmd BufLeave,FocusLost,InsertEnter   * if &nu | set nornu | endif
+  autocmd BufEnter,FocusGained,InsertLeave,WinEnter * if &nu | set rnu   | endif
+  autocmd BufLeave,FocusLost,InsertEnter,WinLeave   * if &nu | set nornu | endif
 augroup END