Add 2020/yang/try.sh + format/typo checks

The Makefile also has been updated with a new rule to compile the C++
code the author provided which can preprocess the output of the program
to make it more acceptable to some compilers.

Format/typo check README.md file.

This should complete 2020! There might be another change in another year
but besides that and the YYYY/README.md files the review of all entries
can be mostly considered done (mostly because I will probably do a very
quick pass but this pass is not important one way or another).

2020/yang/.gitignore

@@ -1,5 +1,6 @@
 #
 # sort with: sort -d -u
+cppp
 *.dSYM
 indent
 indent.c