use caddy 2 for https local development
Created by: ggilmore
Fixes: https://github.com/sourcegraph/sourcegraph/issues/1951
This PR adds a new Procfile entry that runs a https reverse proxy at https://sourcegraph.test:3443
for local dev.
Note that you'll need to have caddy 2 > 2.0.0-beta.19 installed from now on, see https://github.com/sourcegraph/sourcegraph/blob/caddy-local-https/doc/dev/local_development.md#step-5-configure-https-reverse-proxy for installation and configuration instructions.
Note: I tried (for a long time) and failed to get e2e tests working with this. Some combination of web/node/puppeteer doesn't like the self-signed certs and I wasn't able to figure it out. I'll post a WIP PR for @sourcegraph/web to own with my findings after this PR is merged.