data (modify|merge|remove) suggests player selectors

[theusaf]

• From https://github.com/jan00bl/mcfunction-novum/issues/36

• After typing data modify player selectors(@r, @p, @a) are suggested, but the command will result in an error. (Bugs of this type will propably wont be fixed without bigger parsing changes (eg. execute as @p run data merge @s))

  Thank you for your great work! Im feeling quite bad reporting all those bugs, I will try to get into fixing them myself...

While not really an issue for this project yet, I'm leaving this here for future reference.

[theusaf]

May possibly just group this in #20