Make nvim :terminal more consistent with vim

Vim's :terminal feels much more ergonomic, adding various mappings to
make the experience more similar, mainly by adding a few `<C-w>`
mappings for the most common actions.

Additionally, disable vim-tmux-navigators default mappings and setup
both normal and terminal mode mappings for `<C-w>{h,j,k,l}` in addition
to the normal mode mappings for `<C-{h,j,j,l}>` to make the pane
switching experience more consistent across all buffer types.

vimrc

@@ -125,6 +125,7 @@ let g:note_directory = '~/Sync/Notes'
 if !has('win32')
   " Seemless vim/tmux pane navigation
   Pack 'christoomey/vim-tmux-navigator'
+  let g:tmux_navigator_no_mappings = 1
   " Enable focus events when in tmux session
   Pack 'tmux-plugins/vim-tmux-focus-events'
 endif