[jaemk]

Additive over 1.2.0. No API breaks, no migration guide needed.

• Bump the crate version to 1.3.0 and open a fresh [unreleased] changelog section.
• Repin the native-certs doc snippet to 1.3 and regenerate README.md.

Shipping in this release:

• proxy(url) on every Update / ReleaseList builder and on Download, with credentials in the
  URL sent as Proxy-Authorization (add a proxy() setter with credential support #210).
• Error::InvalidProxy { source }, with the proxy password redacted from the error and from every
  Debug rendering (add a proxy() setter with credential support #210).
• extract_file matches ./-prefixed archive entries, so a tar -czf app.tar.gz -C dir . archive
  resolves bin_path_in_archive instead of failing with "Could not find the required path in the
  archive" (match ./-prefixed archive entries in extract_file #211, reported in support tar.gz where files are prefixed by "./" #27).
• The publish workflow runs only for a version that is not yet on crates.io (trigger the publish workflow on an unpublished version #212).

make ci is green.