Allow to run example scripts for grammar from any folder

I computed the parent directory of the scripts with 'dirname'
instead of using '.' and added both this directory and the
parent directory of the 'dirname' command itself to the path
(found by running 'command -v dirname').
Add examples to illustrate compound commands, brace groups, subshells

The brace group and subshell examples reveal a discrepancy in the syntax:
using a similar formal definition in the grammar, brace groups require
an extra delimiter to detect the '}' token while subshells do not have
this requirement to detect the ')' token.
Add examples to illustrate compound lists