Better-Cal: Google Calendar Link Redirect

Rewrites "Add to Google Calendar" links — the buttons on Luma, Eventbrite, Meetup, and countless other event sites — so they open your self-hosted Better-Cal calendar with the event details pre-filled, instead of Google Calendar. Set your Better-Cal's address once in the extension's options (it opens on install). Until an address is set, nothing is redirected. "Stop redirecting" in the options, or toggling the extension off, restores Google Calendar. The redirect happens at the network layer using Chrome's declarativeNetRequest rules: no content scripts, no access to page contents, no data collected or transmitted. Only navigations to Google Calendar's "add event" template URLs are affected; Google Calendar's own event pages and normal browsing are untouched. Companion to Better-Cal, a self-hosted calendar (github.com/Oshyan/better-cal). Not useful without an instance of it.