Fix Tests

[lukeed]

What kind of change does this PR introduce?

Fix

Did you add tests for your changes?

meta

Summary

The tests are scaffolding the default template which relies on preact-cli@2.x, which requires that there be a .babelrc file to handle NODE_ENV-dependent modules formatting.

The .babelrc file itself was also broken. See preactjs-templates/default#21.
^ Not required for this PR.

The current preact-cli/babel (and #639) will respond to a test environment automatically, so there'll be no need to ship a .babelrc file.

The Cannot find module "preact-cli/babel" was thrown in testing because we use --cwd while building the test directories (for performance / to avoid npm install xN). When this happens, dependency lookups are done from the root directory.

Well, the root directory doesn't have preact-cli as devDependency ... only the test directory does. Because of that, the process can't find a module named "preact-cli"; let alone a entry file within it.

Does this PR introduce a breaking change?

No