Add function to get the total xp points the bot has.

[zisis912]

Unlike its title, the bot.experience.points property does NOT provide one with the xp points the bot has, but rather its score, displayed only when one dies.

This PR adds a function that does precisely that, correctly get the bot's xp points.

That of course would make the .points property useless, so I would suggest you accept https://github.com/PrismarineJS/mineflayer/pull/3125 too if backwards compatibility is not an issue

[rom1504]

/fixlint

[rom1504bot]

I fixed all linting errors with npm run fix!

[rom1504]

@zisis912 please fix the lint with above command

[rom1504]

actually fixed

please add this function to the doc

[rom1504]

@zisis912 would you like to finish this?

[zisis912]

I am a bit busy yhese days, maybe in a few docs i will get around to making docs for all of my PRs so they can be finished.