Merge pull request #889 from adam-p/no-permissions

minimize initial permissions

fix: improve HTML sanitization

bump version for release

Merge pull request #875 from adam-p/dev

switch default TeX renderer

switch to fetch for checking for the test file

getLocalFile intentionally doesn't cope with errors, so it was the wrong choice.

This could have been causing real errors on the options page (as `loaded` wasn't being set to true), but I didn't observe any problems.

Merge pull request #870 from adam-p/manifestv3

Support WebExtensions V3

Merge pull request #527 from adam-p/fix-tbird-intl

Fix #524 and #526: Broken in non-English Thunderbird

Merge pull request #520 from adam-p/tbird-fix

Fix #495: Stopped working in Thunderbird 60

Merge pull request #433 from adam-p/firefox-webextensions

Merge WebExtensions changes

Compress zip to be accepted by Chrome store