Update vimrc with plug autoinstall

vimrc

@@ -1,3 +1,9 @@
+if empty(glob('~/.vim/autoload/plug.vim'))
+  silent !curl -fLo ~/.local/share/nvim/site/autoload/plug.vim --create-dirs \
+    https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim
+  autocmd VimEnter * PlugInstall --sync | source $MYVIMRC
+endif
+
 " disable compatability
 set nocompatible