Add plugin category

[michalkleiner]

Description:

Matomo 5.1 will introduce the ability for plugins to add metadata information about belonging to one of the plugin categories: Customisations (customisation), Data management and administration (database), Integrations (integration), Insights (insights), Development (development) or Security (security).

When a new version of a plugin is released with this information after the stable version Matomo 5.1 is released, this category will get picked up by the plugins marketplace and a category specific image will show in the list of plugins, making it easier for users to skim over the list of plugin cards.

We recommended to merge this PR and tag a new version of the plugin after Matomo 5.1 has been released, however, it is not a strict requirement and the information will get picked up by the marketplace with the first version of the plugin released after Matomo 5.1 stable is out.

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed