Add SpecialReportAlt theme article format

[DanielCliftonGuardian]

Co-Authored-By: Ioanna Kokkini [email protected]

What are you changing?

This adds SpecialReportAlt theme in ArticleSpecial.

BREAKING CHANGE: Consumers of ArticleFormat and/or ArticleTheme will need to update to handle this change. This may involve updating component props, fixtures, switch and if statements, etc.

Why?

We need to support a new article type of SpecialReportAlt.

[changeset-bot]

🦋 Changeset detected

Latest commit: 3a2c68e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@guardian/libs	Major
@csnx/npm-package	Patch

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[joecowton1]

Left a comment to this effect in the code, but i'm interested in whether this actually is a breaking change: if we're just adding a new type of theme will that break anything? My gut feeling is that consumers should be fine to continue as they were without it effecting anything.

[ioannakok]

Thanks for your comment @joecowton1! From a quick look in the DCR codebase, it seems there are places where we switch over format.theme without having a default case, e.g.
https://github.com/guardian/dotcom-rendering/blob/main/dotcom-rendering/src/web/lib/decidePalette.ts#L202-L217

At the moment TS is not complaining but we have a PR to fix this: guardian/dotcom-rendering#6105 hence why we think this is a breaking change.

[oliverlloyd]

It's true that this change could cause some consumers to break, so it is breaking in this (important!) sense. Arguably though, we should probably look to update this code to be more resilient and allow these sorts of changes to go out as features, which perhaps, semantically, they are?