port-amd64/56908: links: enable brotli support

[mydeardiary%sdf.org@localhost]

>Number:         56908
>Category:       port-amd64
>Synopsis:       links: enable brotli support
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          doc-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jul 02 16:15:00 +0000 2022
>Originator:     My Dear Diary
>Release:        9.1
>Organization:
SDF users
>Environment:
NetBSD rie 9.1 NetBSD 9.1 (GENERIC) #0: Sun Oct 18 19:24:30 UTC 2020  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
brotli is a new compression algorithm capable of compressing web pages. Most of pages served by cloudflare will be compressed with brotli if the client sends Accept-Encoding: br

Links-browser has the capability of displaying brotli compressed web pages if linked with brotli.
>How-To-Repeat:
Just view the browser request header.
1. On a terminal, start nc with empty http response, i.e. `printf "HTTP/1.1 200 OK\r\n\r\n" | nc -l 9000`
2. On another terminal, launch links and open http://localhost:9000
3. Notice that there is no br string in the Accept-Encoding field.

>Fix:
Add brotli/librotli as dependency for links package.