Addressed CRAN issues

Fixes an issues flagged by Kurt Hornik via email: 2022-02-17:

RLumCarlo::RLumCarlo-package.Rd: Warning: attribute "width" has invalid value "50px"

R CMD check --as-cran results

0 errors | 0 warnings | 0 note

Win-builder flagged a potentially invalid DOI mentioned in the DESCRIPTION:

"(Jain et al. (2012) doi:10.1088/0953-8984/24/38/385402"

This DOI is correct.