Update docs for site-packages

[KitStarLee]

The document states that “By default, Serious Python expects Python dependencies installed into pypackages directory in the root of app directory. You can add additional paths to look for 3rd-party packages using modulePaths parameter”

But in the code，Only Pyodide will use the pypackages folder ？ why??
if (platform != "Pyodide") { if (Platform.environment .containsKey(sitePackagesEnvironmentVariable)) { sitePackagesRoot = Platform.environment[sitePackagesEnvironmentVariable]; } sitePackagesRoot = path.join(tempDir.path, defaultSitePackagesDir); if (sitePackagesRoot == null || sitePackagesRoot.isEmpty) { sitePackagesRoot = path.join(currentPath, "build", "site-packages"); } } else { sitePackagesRoot = path.join(tempDir.path, defaultSitePackagesDir); }

[FeodorFitsner]

That was changed in the last version. To speed up application start as no large archive should be unarchived.