Hi,
If you need isolation between mains and PIC a transformer is a good choice.
Be aware, that a transformer is not an ideal voltage converter, especially the small wattage ones.
Maybe a (small resistive) load at transformer secondary can improve performance. Depends on transformer.
Bridge rectifier is ok. Connect it's negative output to PIC ground.
The rectifier needs about 1.2 of voltage drop to operate. Consider this for desired accuracy.
A single capacitor will measure peak voltage. Mains voltage usually is a bit flat at the top, so it is not pure sine and thus the factor 1.414 will not be exact. Additionally the peak voltage includes all noise, therefore overtones may reduce accuracy.
If you connect a relatively low ohmic resistor at the rectifier output and create a relatively high impedance filter (consider second order low pass) creates an (more) average signal instead of peak signal. Average will be more reliable than peak voltage.
Calibration is needed in either case.
Voltage divider and filter may be combined to reduce part count.
5V corresponds to 220V AC
I don't recommend to use VCC as voltage reference, because VCC is not that precise, not clean and it may drift with load, temperature and time...
You measurement precision depends fully on VCC precision.
If your measurement saturates at 220V input you can not be sure if it is really 230V or even higher.
I recommend to include some headroom. Expand your AC input range at least 20% more than nominal value.
Klaus