allow changes in display format

plugins/timer/timer.plugin.zsh

@@ -4,9 +4,9 @@ __timer_current_time() {
 
 __timer_format_duration() {
   local mins=$(printf '%.0f' $(($1 / 60)))
-  local secs=$(printf '%.1f' $(($1 - 60 * mins)))
+  local secs=$(printf "%.${TIMER_PRECISION:-1}f" $(($1 - 60 * mins)))
   local duration_str=$(echo "${mins}m${secs}s")
-  echo "\`${duration_str#0m}"
+  echo "${TIMER_SYMBOL:-\`}${duration_str#0m}"
 }
 
 preexec() {