docs($interpolate) fix sample code appearing unformatted

Closes #6418
chore(core): introduce a wrapper for requestAnimationFrame
chore(core): create a wrapper to manage async callbacks
perf($animate): use rAF instead of timeouts to issue animation callbacks
docs(guide/concepts): reference correct module name.

Fixed a mistake, changed invoice to invoice2.

Closes #6438
fix($animate): ensure all animated elements are taken care of during the closing timeout

Closes #6395
test($animate): ensure staggering timeout tests are secure