* test: add 'yarn test' GitHub action for PR to main
* fix: run 'tsc build' before 'yarn test'
* fix: missing import in github-client.ts
* chore: in GH Actions, skip tests requiring fiddle
* chore: rename task as "unit tests"
* test: integration tests use a fake electron-fiddle
We don't have electron-fiddle on GitHub Actions, so add a fake that
outputs pre-recorded logs from the real electron-fiddle.
* fixup! test: integration tests use a fake electron-fiddle
* fix: omit platform-specific args from canned logs
* fix: still finding portable checksum for test argv
* chore: rename workflow: 'unit tests' => 'tests'
* fix oops in 1b14ea
* chore: experiment with adding coveralls
* chore: one coverage file for top-level 'yarn test'