Document caveats of match_prev_cmd strategy

This strategy relies on the history being exactly in the order in which
commands have been entered.  Therefore, options like suppressing
duplicates or expiring duplicates first will lead to unexpected
suggestions.

src/strategies/match_prev_cmd.zsh

@@ -16,6 +16,9 @@
 # will be 'ls foo' rather than 'ls bar' because your most recently
 # executed command (pwd) was previously followed by 'ls foo'.
 #
+# Note that this strategy won't work as expected with ZSH options that don't
+# preserve the history order such as `HIST_IGNORE_ALL_DUPS` or
+# `HIST_EXPIRE_DUPS_FIRST`.
 
 _zsh_autosuggest_strategy_match_prev_cmd() {
 	local prefix="$1"