rc: add trigger-user-hook after ansi render

[losnappas]

Can we add this, so I can deduce from elsewhere what got painted last

[krobelus]

why do you need to deduce that? It should already be implied by the hook ordering you defined?
i.e. when you call ansi-enable versus other hooks

[losnappas]

I need it for repls, like described in https://discuss.kakoune.com/t/kakoune-repl-buffer-a-new-way-to-work-with-repls/1435/7

if the cursor is after the end of the last chunk, all the text from the end of the chunk up to the cursor is sent to the REPL as input

To track the end of the last chunk, after any BufReadFifo renders more ansi encoded characters.

[eraserhd]

I'm not sure you really need this, but I'm OK with it.

Beware that there are currently issues if escape sequences get split between chunks. The state currently gets lost at the end of the chunk, so the next chunk starts out visible even if it is a continuation of an escape sequence.