Add quote autocompletion for previous messages

Fixes https://github.com/profanity-im/profanity/issues/1649

Type `>` then press tab or shift tab to autocomplete previous messages,
then type your reply and send message.
Newlines are replaced with newline followed by `> `.
A newline is added at the end so that the user can immediately type a
message without manually adding a new line.

src/ui/chatwin.c

@@ -323,6 +323,7 @@ chatwin_incoming_msg(ProfChatWin* chatwin, ProfMessage* message, gboolean win_cr
     }
 
     wins_add_urls_ac(window, message);
+    wins_add_quotes_ac(window, message->plain);
 
     if (prefs_get_boolean(PREF_BEEP)) {
         beep();
@@ -346,6 +347,9 @@ chatwin_outgoing_msg(ProfChatWin* chatwin, const char* const message, char* id,
 {
     assert(chatwin != NULL);
 
+    ProfWin* window = (ProfWin*)chatwin;
+    wins_add_quotes_ac(window, message);
+
     char* enc_char;
     if (chatwin->outgoing_char) {
         enc_char = chatwin->outgoing_char;