[#341] Added disable and single icon flags to text-icon.

[alan-cole]

Checklist before requesting a review

• [x] I have formatted the subject to include the issue number as [#123] Verb in past tense with a period at the end.
• [x] I have provided information in the Changed section about WHY something was done if this was a bespoke implementation.
• [x] I have performed a self-review of my code.
• [x] I have commented on my code, particularly in hard-to-understand areas.
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [x] I have run new and existing relevant tests locally with my changes, and they have passed.
• [x] I have provided screenshots, where applicable.

Changed

1. Added icon_group_disabled and icon_single_only flags to text-icon. This will allow for grouping to be disabled, and for external links to display in-place of icons.
2. Applied the use of the new settings to cards that were using non-standard styling of links with icons. They include: navigation-card, next-step, publication-card and subject-card.

Screenshots

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🚀 Deployed on https://66ff921890696cb91ba3697f--civictheme-uikit.netlify.app

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 13.87%. Comparing base (7315692) to head (3cd915e). Report is 4 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #403 +/- ## ======================================= Coverage 13.87% 13.87% ======================================= Files 27 27 Lines 1290 1290 Branches 307 307 ======================================= Hits 179 179 Misses 894 894 Partials 217 217 ```

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[richardgaunt]

Fixes #341