www/ruby-html-proofer: update to 3.19.1

There are a few note with release but not others.  Please refer commit log
<https://github.com/gjtorikian/html-proofer/compare/v3.15.2...v3.19.1> in
detail.

3.19.1 (2021-04-18)

3.19.0 (2021-04-11)

* Support hydra config on CLI #632

3.18.8 (2021-03-04)

3.18.7 (2021-03-04)

3.18.6 (2021-02-21)

3.18.5 (2021-01-02)

3.18.4 (2021-01-02)

3.18.3 (2020-12-29)

3.18.2 (2020-12-17)

3.18.1 (2020-12-16)

3.17.2 (2020-11-23)

3.17.1 (2020-11-22)

3.17.0 (2020-11-14)

3.16.0 (2020-09-10)

* Add support for before_request: #577

3.15.3 (2020-04-20)

(taca)