Improve rendering of the output

[s-heppner]

Currently, the output works fine and is readable, but could be improved upon:

Entry 'iec61360-1-2017' of type 'standard' failed verification:
  ❌ Invariant Violations:
    - Entry 'iec61360-1-2017' contains the non-allowed field: [url]. Move the content of the field into the [note] field.
    - Entry 'iec61360-1-2017' contains a malformed field [note]. Make sure the [note] field follows the following pattern: '[ONLINE]. Available: \url{...}, Accessed: YYYY-mmm-dd'
    - Entry 'iec61360-1-2017' misses the following required fields: [organization]
    - Entry 'iec61360-1-2017' misses required field [organization]. This should be the issuing body or standards organization.
    - Entry 'iec61360-1-2017' fields [author] and [organization] are the same. Remove field [author].

• We can remove one of the indentation levels (❌ Invariant Violations:)
• We do not need to state the entry name at each violation since it is mentioned already above.