Add documentation info to the README.md
At adi_hdl_parser.py, filter "_signal_clock" and "_signal_reset"
pseudo buses from component.xml files, append them as description
in the ports table, in the format
"{Bus} [...] is synchronous to this {domain}".
Also, adds collapsible directive
Signed-off-by: Jorge Marques <jorge.marques@analog.com>