Feature request: support for @software bibtex records for citing ASCL codes

[kirxkirx]

Would it be possible to add support for @software bibtex records for citing codes from the Astrophysics Source Code Library (ASCL)? For example, I'm citing the ASCL record for Fermitools that I got from the ADS:

@software{2019ascl.soft05011F,
       author = {{Fermi Science Support Development Team}},
        title = "{Fermitools: Fermi Science Tools}",
 howpublished = {Astrophysics Source Code Library, record ascl:1905.011},
         year = 2019,
        month = may,
          eid = {ascl:1905.011},
       adsurl = {https://ui.adsabs.harvard.edu/abs/2019ascl.soft05011F},
      adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}

Unfortunately, when running on my paper source the adstex reports

Entry type software not standard. Not considered.

and ignores this record, so I have to insert it manually in the .bib file every time I re-reun adstex, which is a minor, but seemingly unnecessary inconvenience.

[yymao]

Thanks for the report. I am working on a fix in #43