Ubuntu 18.04 provides libvpx5 while Ubuntu 20.04 does libvpx6

libssl-dev is provided with the stack image in build time and
conflicts in building openssl Gem for webauthn Gem added with #14466.

UWS needs openssl and zlib https://github.com/uNetworking/uWebSockets/wiki/Misc.-details#dependencies

It seems libicu-dev no longer installs libicu55 needed by charlock_holmes.

Fix builds that fail on Heroku.

* Specs for language detection

* Use CharlockHolmes instead of NKF

* Correct mistakes

* Correct style

* Set hint_enc instead of falling back and strip_tags

* Improve specs

* Add dependencies

This change adds mp4 support confirmed on Heroku-16 stack.

Use https://github.com/heroku/heroku-buildpack-apt to
install protobuf-compiler and libprotobuf-dev which are needed by cid3