[hq9+] Added manual for HQ9+ programming language (#2431)

hq9+.html.markdown

@@ -0,0 +1,38 @@
+---
+language: HQ9+
+contributors:
+    - ["Alexey Nazaroff", "https://github.com/rogaven"]
+---
+
+HQ9+ is a joke programming language created by Cliff Biffle. It has only four commands and it isn't Turing-complete.
+
+```
+There is only 4 commands, represented by next characters
+H: print "Hello, world!"
+Q: print the program's source code (a Quine)
+9: print the lyrics to "99 Bottles of Beer"
++: add one to the accumulator (the value of the accumulator cannot be accessed)
+Any other character is ignored.
+
+Ok. Let's write some program:
+  HQ9
+
+Result:
+  Hello world!
+  HQ9
+
+HQ9+ is very simple, but allows you to do some things that are very difficult
+in other languages. For example, here is a program that creates three copies of
+itself on the screen:
+  QQQ
+
+This produces:
+  QQQ
+  QQQ
+  QQQ
+```
+
+And that's all. There are a lot of interpreters for HQ9+. Below you can find one of them
+
++ [One of online interpreters](https://almnet.de/esolang/hq9plus.php)
++ [HQ9+ official website](http://cliffle.com/esoterica/hq9plus.html)