docs: suggest alternatives to xip.io

Fixes #1887

README.md

@@ -115,7 +115,7 @@ For each host defined into `VIRTUAL_HOST`, the associated virtual port is retrie
 
 ### Wildcard Hosts
 
-You can also use wildcards at the beginning and the end of host name, like `*.bar.com` or `foo.bar.*`. Or even a regular expression, which can be very useful in conjunction with a wildcard DNS service like [xip.io](http://xip.io), using `~^foo\.bar\..*\.xip\.io` will match `foo.bar.127.0.0.1.xip.io`, `foo.bar.10.0.2.2.xip.io` and all other given IPs. More information about this topic can be found in the nginx documentation about [`server_names`](http://nginx.org/en/docs/http/server_names.html).
+You can also use wildcards at the beginning and the end of host name, like `*.bar.com` or `foo.bar.*`. Or even a regular expression, which can be very useful in conjunction with a wildcard DNS service like [nip.io](https://nip.io) or [sslip.io](https://sslip.io), using `~^foo\.bar\..*\.xip\.io` will match `foo.bar.127.0.0.1.xip.io`, `foo.bar.10.0.2.2.xip.io` and all other given IPs. More information about this topic can be found in the nginx documentation about [`server_names`](http://nginx.org/en/docs/http/server_names.html).
 
 ### Multiple Networks