Fix punctuation, spelling, grammar and GDScript style guide compliance in vr_starter_tutorial. Remove duplication.
"a" becomes "an" before vowel sound.
Do **NOT** use ["different" after "various"](https://www.thefreedictionary.com/various)!
Fix punctuation and grammar in vr_primer.
"then" < When?
"than" < Compared to what?
"acceptable" (adjective) = the nature of an object/thing;
"acceptably" (adverb) = the nature of an action/process.
Fixed formatting and corrected the example code to better reflect the intent of the tutorial text.
i.e. "...The last thing we are doing in button_pressed is checking to see if the button pressed is 1..."
* Added a starter VR tutorial.
The VR tutorial covers the basics of making a VR game, along with making a teleportation system,
a RigidBody pick-up/drop system, and a few different special RigidBody nodes.
