fix(no-single-variables-to-translate): allow top-level calls to plural/select/selectOrdinal

[jtbandes]

Fixes #126

This PR updates the no-single-variables-to-translate logic to explicitly allow syntax like msg`${plural(...)}`, which seems to be the recommended way to do plural messages with a custom i18n instance (outside of JSX), according to this discussion: lingui/js-lingui#1312 (comment)

[jtbandes]

Hi @timofei-iatsenko, any interest in this patch?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.13%. Comparing base (05d7ae4) to head (b72abf3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #133      +/-   ##
==========================================
+ Coverage   98.11%   98.13%   +0.02%     
==========================================
  Files          13       13              
  Lines         636      643       +7     
  Branches      214      220       +6     
==========================================
+ Hits          624      631       +7     
  Misses         12       12              

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[andrii-bodnar]

Looks good to me, thanks for the contribution!

@timofei-iatsenko WDYT?

[jtbandes]

Friendly bump :)