vim:fzf: Span fzf over full window in tmux

Use tmux popup windows for fzf in vim, so that it spans (almost) the
full tmux window. My use-case for this is, that sometimes I open fzf in
a split pane and notice then that the lines are too long for the width
of the pane. Since the fzf window won't resize if I resize the pane
(TODO: issue in fzf.vim), I have to first close it, resize and then
reopen fzf. I hope to fix this by using always the big tmux popup and
eliminating the need to resize at all. The issue remains when vim is in
a split window outside of tmux. I can imagine that this will become
annoying, but we'll see...

.config/vim/vimrc.d/50-looks.vim

@@ -41,8 +41,13 @@ if (get(g:, 'loaded_fzf'))
 	" Use a theme for bat in the preview that somewhat resembles onedark
 	let $BAT_THEME='TwoDark'
 
-	" Increase size of fzf window
-	let g:fzf_layout = { 'window': { 'width': 0.95, 'height': 0.9 } }
+	" Increase size of fzf window and make it span over full window when in
+	" tmux
+	if exists('$TMUX')
+		let g:fzf_layout = { 'tmux': '95%,90%' }
+	else
+		let g:fzf_layout = { 'window': { 'width': 0.95, 'height': 0.9 }}
+	endif
 endif
 
 " Highlight trailing whitespaces