[hdl/en] "hdl" is not a specific language

The [page on hdl](https://learnxinyminutes.com/docs/hdl/) is great to have, but it's a bit confusing to me because **HDL is not a language; it's a family of languages--VHDL and Verilog** being what someone is referring to the overwhelming majority of the time when they say "HDL". There is no mention of either VHDL or Verilog on the page itself, but in the resource links at the bottom, there is of course the Wikipedia page saying exactly what I said: HDL is a type of language, not a language.

It's like if there was a page on the site just for object-oriented programming, and all the code was written in Java, but there was no mention of the fact that it was Java, or even that Java was just a language that falls under OOP.

Open the page on hdl linked in the issue and review its text alongside the resource links. Clarify that HDL is a family of languages and mention VHDL and Verilog on the page; done when readers can distinguish the category from the specific languages without relying on the external Wikipedia link.

Written by the indexing model from the issue text.