refactor: handle $0 according to the Zsh plugin standard (#10518)

For details and rationale, see:
https://zdharma-continuum.github.io/Zsh-100-Commits-Club/Zsh-Plugin-Standard.html

Closes #10518

plugins/emotty/emotty.plugin.zsh

@@ -10,6 +10,11 @@
 # % export emotty_set=nature
 # ------------------------------------------------------------------------------
 
+# Handle $0 according to the standard:
+# # https://zdharma-continuum.github.io/Zsh-100-Commits-Club/Zsh-Plugin-Standard.html
+0="${${ZERO:-${0:#$ZSH_ARGZERO}}:-${(%):-%N}}"
+0="${${(M)0:#/*}:-$PWD/$0}"
+
 typeset -gAH _emotty_sets
 local _emotty_plugin_dir="${0:h}"
 source "$_emotty_plugin_dir/emotty_stellar_set.zsh"