build: Updated @eyeo/webext-sdk dependency to 0.8.0 [#1317]

This MR contains the following changes:

• Updated vendor/webext-sdk dependency to 0.8.0.
• Added required "declarativeNetRequestFeedback" permission.
• Made notifications API usage asynchronous.
  • Locally cache ignored notifications categories to keep interactions with "ignored_notifications" pseudo-preference synchronous, thereby avoiding significant changes to the UI and/or the Messaging API.
• Updated documentation accordingly.
  The documentation of EWE's Suscription object wasn't updated (see https://gitlab.com/eyeo/adblockplus/abc/webext-sdk/-/issues/455), so the changes were made based on what's mentioned in the release notes and observations during implementation.

This MR also contains the following unrelated changes:

• Replaced "declarativeNetRequest" with "declarativeNetRequestWithHostAccess" permission in preparation for future changes to host permissions. Those permissions are expected to be equivalent for the time being, as long as we have the "<all_urls>" host permission.

This MR does not contain adjustments to the rules (see #1327 (closed)) or the UI (see #1328 (closed)) that aren't required for updating the dependency.