Update README with link to the commands reference. Remove obsolete readme parts.

[carbolymer]

Changelog

- description: |
    Update README with link to the commands reference. Remove obsolete readme parts.
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  # - breaking       # the API has changed in a breaking way
  # - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  # - refactoring    # QoL changes
  # - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
   - documentation  # change in code docs, haddocks...

Context

Rendered

• https://github.com/IntersectMBO/cardano-cli/blob/mgalazyn/chore/update-readmes/README.md
• https://github.com/IntersectMBO/cardano-cli/blob/mgalazyn/chore/update-readmes/cardano-cli/README.md

Checklist

• [x] Commit sequence broadly makes sense and commits have useful messages
• [ ] New tests are added if needed and existing tests are updated. See Running tests for more details
• [x] Self-reviewed the diff