Set up testing with Vitest and jsdom and add unit tests for importers (jellyfin, playnite, stashapp, xbvr). Add typedoc configuration and update vite.config.ts and importer source files to support the tests. Ignore generated docs by adding /docs to .gitignore and add test-related devDependencies (vitest, @vitest/ui, jsdom, typedoc) in package.json.
