* fix: correct reading of sync-labels input.
Contrary to the assumptions made in the unit tests, core.getInput
always returns a string, and !!'false' is true.
Also updates the unit test to reduce changes of regressions by ensuring
that the mocked getInput returns a string, as it would in production.
Fixes https://github.com/actions/labeler/issues/112
Make sure test catches regressions.
* Rebuild dist/index.js.
