Block requests with type "beacon" or "ping"

[MariagraziaAlastra]

Reviewer: @dharb

Description:

Beacon and ping type requests are slipping through currently, because they're not included in the list of resource types we recognize and block.
However, adding "beacon" to the list errors on Chrome, while "ping" doesn't seem to block anything in Firefox.
With this change we'll add either beacon or ping on extension install/update depending on the browser.
Also add "beacon" as a reason for blocking these requests.

Steps to test this PR:

1. build and reload extension
2. check both firefox and chrome.
3. visit a site that uses beacons (google, youtube, amazon etc) and disable privacy protection
4. in the network tab you should be able to see the beacons loading (usually you can filter by "analytics" to make them show up)
5. enable privacy protection; now the beacon requests should be blocked
6. also run unit tests

Automated tests:

• Unit tests
• Integration tests

Reviewer Checklist:

• Ensure the PR solves the problem
• Review every line of code
• Ensure the PR does no harm by testing the changes thoroughly
• Get help if you're uncomfortable with any of the above!
• Determine if there are any quick wins that improve the implementation

PR Author Checklist:

• Get advice or leverage existing code
• Agree on technical approach with reviewer (if the changes are nuanced)
• Ensure that there is a testing strategy (and documented non-automated tests)
• Ensure there is a documented monitoring strategy (if necessary)
• Consider systems implications

[russellholt]

Looks good; suggested simplification.

[dharb]

Nice work @MariagraziaAlastra ! This looks great.

At some point we should build some new unit tests for trackers.es6 (and maybe make that isTracker function a little more testable) so that we can better test things like trackersByParentCompany.reason. I don't think here is the place or time to do that though.