feat(readme-backend): added config to set the cache ttl

[anicke]

Hey, I just made a Pull Request!

In the "readme-backend" plugin no ttl where configured, this PR sets a default 1 hour ttl and makes it possible to override this using the config.

Issue ticket number and link

• Fixes Readme backend cache is not configurable and therefore caches indefinitely #287 287

Checklist before requesting a review

• I have performed a self-review of my own code
• I have verified that the code builds perfectly fine on my local system
• I have verified that my code follows the style already available in the repository
• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)

[changeset-bot]

🦋 Changeset detected

Latest commit: d7bf11b

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

This PR includes changesets to release 2 packages

Name	Type
@axis-backstage/plugin-readme-backend	Patch
backend	Patch

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[fridajac]

Nice!