Fix minor issues in README.md

[andrew-k-21-12]

It can be reasonable to revisit the overall README.md and rewrite clunky places inside of it.

Some of inaccuracies to be fixed include:

1. Suggested project name and group in Quick start do not fit each other as they should produce org.example.example package name. Project name can be changed into demo, for example, all packages in code listings should be updated correspondingly.
2. It's not strictly required to have either version or main.customBundleStaticsDirectory to generate resource wrappers (it was mentioned in Type-safe resource wrappers generation). Emphasize it somehow or remove such note at all.
3. There is a mistake in the Fonts section: "The second part is super limited now - it can recognize only Light as variant name". While actually it can also recognize Regular font variants - correct it.
4. Provide more intuitive paths (for --source-bundle and --deployment-destination arguments) in the example for frontend-patching-deployer execution command. Use the actual production build output directory and some popular path for placing front-ends — e.g., "public".