This commit adds a separate protected resource page to demonstrate how
to selectively require logins.
Add code to improve client performance by providing modification timestamps
and Cache-Control headers for embedded static files.
- add linter config and fix golangci-lint warnings
- rename module to match new repository location
- use embedded resources for static assets, templates and translations
- recommend mkcert in README
- require at least Go 1.19
- update and tidy dependencies
- update copyright information
- improve Makefile, add lint and static asset targets
