Enhance abstract skill for DITA short descriptions

[Lennonka]

What changes are you introducing?

Enhancing the abstract AI skill with instructions for DITA short descriptions

Why are you introducing these changes? (Explanation, links to references, issues, etc.)

To achieve higher quality of AI work

Anything else to add? (Considerations, potential downsides, alternative solutions you have explored, etc.)

These instructions come from DITA reference.

Contributor checklists

• I am okay with my commits getting squashed when you merge this PR.
• I am familiar with the contributing guidelines.

Please cherry-pick my commits into:

• Foreman 3.18/Katello 4.20 (Satellite 6.19)
• Foreman 3.17/Katello 4.19
• Foreman 3.16/Katello 4.18 (Satellite 6.18; orcharhino 7.6, 7.7, and 7.8)
• Foreman 3.15/Katello 4.17
• Foreman 3.14/Katello 4.16 (Satellite 6.17; orcharhino 7.4; orcharhino 7.5)
• Foreman 3.13/Katello 4.15 (EL9 only)
• Foreman 3.12/Katello 4.14 (Satellite 6.16; orcharhino 7.2 on EL9 only; orcharhino 7.3)
• We do not accept PRs for Foreman older than 3.12.

[github-actions]

The PR preview for 6e341d9 is available at theforeman-foreman-documentation-preview-pr-4814.surge.sh

No diff compared to the current base

show diff

[Lennonka]

Going to test it.

[Lennonka]

TBH, I have no idea if the results are better or worse now... see #4815

@aneta-petrova @jafiala Care to try it out too?