apng2webp: fix delay

apngdis stores the delay as fraction and i used it as if it were in
miliseconds.

.config/zsh/functions/apng2webp

@@ -40,8 +40,9 @@ done
 local -a webpmux_options=()
 local -i counter=1
 for file in apngdis/apngframe*.txt; do
-    local delay=$(grep -Po '=\d+/' ${file})
-    delay=${delay:1:-1}
+    local delay=$(grep -Po '=\d+/\d+' ${file})
+    delay=${delay:1}
+    delay=$(( ( 1000 + ${delay%/*} ) / ${delay#*/} ))
     [[ ${#o_delay} -eq 2 ]] && delay=${o_delay[2]}
 
     webpmux_options+=(-frame $(printf "%03d.webp" ${counter}) +${delay}+0+0+0-b)