Fill out target metadata stanza

[schlafly]

This adds some values to the target metadata stanza. romanisim usually just gets an ra/dec as input, so the only values we can meaningfully fill out are those ra/dec. But there are vaguely reasonable values to which one can set many of the other values as well.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.38%. Comparing base (725b7cb) to head (d909467).
Report is 52 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #103      +/-   ##
==========================================
- Coverage   92.44%   92.38%   -0.06%     
==========================================
  Files          16       16              
  Lines        1509     1576      +67     
==========================================
+ Hits         1395     1456      +61     
- Misses        114      120       +6     

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