feat(previewer): add beforePreview and afterPreview hooks

Status Job ID Name Coverage
failed #339


Name Stage Failure
build_image Test
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the pagedjs@0.1.34 tests script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/node/.npm/_logs/2019-08-22T15_28_18_392Z-debug.log
npm ERR! Test failed. See above for more details.
ERROR: Job failed: exit status 1