Added note about parse_headers()

notes/arch.md

 
     [ STM ]
 
-       | 1      gen_sts(stm,args)   # generate a number of STS from a STM
+       | 1      parse_head()        # parse text and fill out metadata properties
+       |        gen_sts(stm,args)   # generate a number of STS from a STM
        |                            # * stm - STM object
        |                            # * args - args specify ranges from where
        |                            #          STMs are generated; typically