Currently there has property sub-text https://mpv.io/manual/master/#command-interface-sub-text to observe the text of the current sub. It would be nice to have a similar property for the entire subtitle, possibly called sub-text-all

the usage of this feature may be to get the entire embedded subtitle and then translate it and add a translated subtitle track on the fly

Expected behavior of the wanted feature

add a sub-text-all property to return the current entire subtitle as text