Use annotations to present placeholder examples to make code shorter and permit more expressive placeholder annotations

Something like this:

```yaml
- description: Archive specific files
  code: "archive-util {/file archive} {/path input}"
  annotations:
  - 0: # or "archive" (if such description is unique), or even "archive.<index>" (if it's not unique)
    - names: [sample]
    - extensions: [tar]
    - require: [extension]
    - repeat: 1..
  - 1:
    - names: [~/.bashrc]
```