[README] updated info about input format

README.md

@@ -8,4 +8,6 @@
 ```
 CREATE TABLE presenze (ID INTEGER PRIMARY KEY AUTOINCREMENT, checkin TEXT, codfis TEXT, anagrafica TEXT);
 CREATE TABLE sqlite_sequence(name,seq);
-```
+```
+## Formato tessera
+```_AAAAAAAAAAAAAAAA_COGNOME  NOME1 NOME2_```