Update webext-sdk dependency to 0.2.0

Background / User story

We updated the webext-sdk dependency to 0.1.1 in #1060 (closed) in order to bring in all the changes that we required to fully integrate EWE into Adblock Plus. Before we release it though, we should update it to 0.2.0, so that we use a version of EWE that's ready to release to users and that fixes all the problems that we find during Feature QA.

Dependency changes

Name: webext-sdk
New version: 0.2.0
Breaking changes: None
Other changes:
- ewe#142 - Updated adblockpluscore to 0.6.0.
  - core#369 - Added support for :not() selector to element hiding emulation filters.

Integration changes

Legal: N/A
Development: None

Hints for testers

Disabled filters subscription error message should behave as expected (incl. comment filters should not be treated as disabled filters).

Open topics

Issue	Description	Status
eyeo/adblockplus/abc/webext-sdk#143 (comment 850068653)	check whether change should be pushed back further, due to continued lack of a compatible abp-snippets dependency	✓
eyeo/adblockplus/abc/webext-sdk#183 (closed)	add URL to snippet filter hits for #1096 (closed)	✓
#1092 (closed)	check whether reported security issue requires changes in EWE	✓