[nvim] Add useful writing colorscheme

Pencil is from reedes, cribbed from iWriter. It is a good, subdued
colorscheme for writing prose. All colorschemes in this vimrc now come
with italicized letters (for comments, and words that should be italic).
All themes also respect the background= dark/light distinction and
enable the respective mode.

.config/nvim/init.vim

@@ -114,6 +114,7 @@ Plug 'edkolev/tmuxline.vim'
 " Colorschemes
 Plug 'morhetz/gruvbox'
 Plug 'rakr/vim-one'
+Plug 'reedes/vim-colors-pencil'
 
 call plug#end()
 endif
@@ -386,9 +387,14 @@ let g:ale_linters = {
 let g:airline_powerline_fonts=1
 let g:airline_theme='raven'
 
+" Enable italics for colorschemes that support them
 let g:gruvbox_italic=1
+let g:one_allow_italics=1
+let g:pencil_terminal_italics=1
+
 colorscheme gruvbox
 
+
 " disable automatically refreshing the mux statusbar since it breaks tmux
 " prefix highlighting. Instead, when changing vim statusbar just create
 " snapshot with :TmuxlineSnapshot file and stick it into tmux config manually