docs: update README with configuration options

docs: change URL for configuration options

Mozilla doesn't allow you to use <pre></pre> in their page, so it's
better to refer the README.

fix: set the correct extension ID provided by Mozilla

build: release 0.2.0

refactor: add and run Prettier

feat: trigger a different org-protocol URL based on the website

A simple configuration UI was added to support this.

The user could, for example, trigger a different template if he's trying
to bookmark a book, or if he's trying to bookmark a video.

feat: change icons to support dark/light themes

initial commit