Update README.md

[seannam1218]

• Remove mass-based article link. Link is dead.
• Rearrange words to improve readability. "Items can be configured to be picked up at any point, or when grabbed, can rotate and position themselves to match a predefined orientation." -> "Items can be configured to retain their orientation when grabbed, or rotate and position themselves to a predefined orientation."
• "...option to dynamically let the controllers turn into physical objects..." -> "...option to dynamically turn the controllers into physical objects..."

[bkt161616]

Oui