Coverage in the frontend package

[wesleybl]

Add a make coverage command to the root of the frontend addon repository to run tests analyzing test coverage.

[wesleybl]

I tried this with the current Jest configuration, but it didn't work. Jest only computes coverage for files inside <rootDir>. See:

jestjs/jest#3053

In the current frontend addon configuration, since tests are run in the Volto context, with the command:

RAZZLE_JEST_CONFIG=$(pwd)/jest-addon.config.js pnpm --filter @plone/volto test -- --passWithNoTests

<rootDir> is the core/packages/volto folder. But since the addon code is outside this folder, Jest doesn't compute coverage for these files, even when we use collectCoverageFrom. The test coverage is zero.

Since the trend now is to use vitest, we can try to compute coverage there.