Currently, eventual isotopes cannot be annotated

[Adafede]

Is your feature request related to a problem? Please describe.
I'm always frustrated when I know a fragmented species corresponds to, for example, [+1M+H]+ instead of [M+H]+ but I cannot take this information into account

Describe the solution you'd like
In such case, shift the masses for both MS1 and MS2 annotations.

Describe alternatives you've considered
Not allowing such weird things and fragment the correct species instead

Additional context
Try to look at the best notation for such species

[Adafede]

Also linked to #141

[Adafede]

Should be done, just needs checks with actual examples

[Adafede]

Linked to HUPO-PSI/mzTab#211