Fix Go websocket tutorial link

[morning-verlu]

Fixes the broken README link for the Go realtime chat tutorial by pointing it to an archived copy of the original article.

Closes #859.

Validation:

• curl -L -o /dev/null -s -w 'old %{http_code} %{url_effective}\n' https://www.thepolyglotdeveloper.com/2016/12/create-real-time-chat-app-golang-angular-2-websockets/ -> 404
• curl -L -o /dev/null -s -w 'new %{http_code} %{url_effective}\n' https://web.archive.org/web/20260214230813/https://www.thepolyglotdeveloper.com/2016/12/create-real-time-chat-app-golang-angular-2-websockets/ -> 200
• git diff --check -> passed