Lataa Algernon 1.17.12

- Improve value conversions in Lua, ref #119.
- Improve the experimental WebAuthn support.
- Add the --strict-symlinks flag, for not following symlinks that lead out of the served directory.
- Add htmlescape and use it in serverconf.lua.
- Keep the server log and the access logs open, instead of opening and closing them for every line + improve log rotation abilities.
- Rewrite the reverse proxy to use httputil.ReverseProxy.
- Only look ahead at proxied responses that have a Content-Length.
- Also log requests that are handled by a reverse proxy.
- Store Let's Encrypt certificates in $XDG_DATA_HOME/certmagic, $HOME/.local/share/certmagic or /var/lib/algernon.
- When using --domain, also serve the localhost directory for the current IP addresses.
- Add the --dirbaseurl flag, for placing a base URL in front of the links in the directory listing, ref #90.
- Add the SetDirBaseURL Lua function that can be used from serverconf.lua, for the same purpose as --dirbaseurl.
- Replace the graceful package with http.Server.Shutdown from the standard library.
- Set new log files to mode 0640.
- Reject AddReverseProxy endpoint URLs that have no scheme or host.
- Improve how certmagic-related events are logged.
- Improve how --letsencrypt starts and retries.
- Update dependencies.
- Update documentation.