Implement set.js snippet

With the recent changes with youtube ads, json-prune isn't enough to block preroll ads.

We're using the following set constant snippet to nullify part of the youtube script:

youtube.com##+js(set, ytInitialPlayerResponse.adPlacements, undefined)
youtube.com##+js(set, adPlacements, undefined)

Without set being used, the user will experience a white screen ad-overlay (basically part of an Ad pre-roll).

What to change

• Implement the override-property-read snippet.

#edit. Just to give credit, where credit is due.

Sorry for not stating, have to give credit to uBO devs / Raymond Hill for implementation of set.js feature. Without this snippet (and other snippets) our options to control youtube ads would be limited