* Support for Thunderbird

* Support for configuring the service for rendering formulas (not fully operational)

* Options can be reset to default

* Support for user configured macros for common subformulas

* Updated integrated MathQuill version to 685bda1

* Updated jQuery to version 3.6.0

* Supporting Google Inbox (http://inbox.google.com)

* Supporting \mathcal for script font, \cases for cases

* Created a Chrome version of the plugin (needs a slightly different manifest.json)
* Bugfix: Removed blue border around web-pages.
* Icon for extension is now a PNG (SVG not supported by Chrome).