signs eat backslashes

[Niklp09]

write a sign containing "\", it's displayed properly, but when you edit it again, formspec treating them as escapes and they disappear

yl issue: https://gitea.your-land.de/your-land/bugtracker/issues/5016

[OgelGames]

Looks like it's missing a minetest.formspec_escape(), which is bad 👀

display_modpack/signs_api/init.lua

Line 32 in e0e0305

meta:set_string("display_text", text)

display_modpack/signs_api/init.lua

Lines 62 to 63 in e0e0305

	fs = "textarea[0.5,0.7;5.5,2;display_text;"..F("Text")..""..
	extralabel..";${display_text}]"

Only problem is you can't just escape the text before saving it in display_text, because that string is also used for creating the entities, so you would see the escapes.