Add pc.Application#enableVr and pc.Application#disableVr (playcanvas#…

…1683)

* Add pc.Application#enableVr and pc.Application#disableVr functions for developers to control VR capabilities
* Remove application argument to enable vr.

Rtl alignment fix (playcanvas#1678)

* fixed text alignment

Removed call to typedarray map (playcanvas#1642)

* added preUpdateHook

* replaced typedarray.map with constructor

[FIX] Missing 'chunks' from a previous PR

Font padding fix fix (playcanvas#1606)

[FIX] Particle system component now listens on all asset events (play…

…canvas#1603)

A hotfix for sprites batching drawOrder (playcanvas#1594)

Library code assets (playcanvas#1566)

* Set asset to loaded if it's a library script

Text-element render sub-range (playcanvas#1585)

* added text-element sub-range
* using two separate properties for range start and end
* expose range start and end in ElementComponent
* small doc update