fix: allow for permsRepo without repository

[bcoe]

If someone publishes their first package with only repoPerms, it's not possible to publish again.

[codecov]

Codecov Report

Merging #79 into master will increase coverage by 0.35%.
The diff coverage is 78.57%.

@@            Coverage Diff             @@
##           master      #79      +/-   ##
==========================================
+ Coverage   29.03%   29.39%   +0.35%     
==========================================
  Files          18       18              
  Lines        2228     2245      +17     
  Branches      105       94      -11     
==========================================
+ Hits          647      660      +13     
- Misses       1581     1585       +4     

Impacted Files	Coverage Δ
src/lib/packument.ts	47.85% <72.72%> (+1.40%)	⬆️
src/lib/write-package.ts	73.41% <82.35%> (+0.12%)	⬆️

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