Update documentation for beam stripping
The documentation for beam stripping interactions has to be updated after some code modifications
- Residual gas interactions have been extended in case of incident
H2P
andDEUTERON
through a new cross section function (OPAL/src#665 (closed)) - Beam stripping is now available in OPAL-t after modified
VACUUM
element (OPAL/src#684 (closed))