feat: check for eza for LIST_COMMAND option

The `exa` project is unmaintained and development moved the `eza` fork, but as
of 1707207983, `eza` does not release prebuilt macOS binaries unlike `exa`. To
avoid unnecessarily breaking user configurations, `exa` has not been removed.

zinit.zsh

@@ -65,6 +65,8 @@ fi
 if [[ -z ${ZINIT[LIST_COMMAND]} ]]; then
     if (( ${+commands[exa]} )); then
         ZINIT[LIST_COMMAND]='exa --color=always --tree --icons -L3'
+    elif (( ${+commands[eza]} )); then
+        ZINIT[LIST_COMMAND]='eza --color=always --tree --icons -L3'
     elif (( ${+commands[tree]} )); then
         ZINIT[LIST_COMMAND]='tree -L 3 -C --charset utf-8'
     else