Fix init of ContentHighlightAsset

[yurabakhtin]

What kind of change does this PR introduce? (check at least one)

• Bugfix

The PR fulfills these requirements:

• It's submitted to the develop branch, not the master branch if no hotfix
• All tests are passing
• Changelog was modified

Other information:
https://github.com/humhub/humhub-internal/issues/89#issuecomment-2110317971
#6971

[what-the-diff]

PR Summary

• Dependency Added to ContentAsset
  Our software now contains a new dependency within 'ContentAsset'. The humhub\modules\content\assets\ContentHighlightAsset has been added, allowing for better interaction between different parts of the project.

• Change in ContentHighlightAsset Registration
  Previously, the practice was to register humhub\modules\content\assets\ContentHighlightAsset from within 'Events::onViewBeginBody'. This step has been eradicated to streamline the process.

• Addition of 'init' method in ContentHighlightAsset
  The ContentHighlightAsset::init method has been integrated, providing us the ability to register the content.highlight JS config. This means it's easier for the software to know how to work with content.highlight data.

• Removal of the Begin Body Event Registration
  The registration of View::EVENT_BEGIN_BODY event via Events::onViewBeginBody in config.php was removed. This change contributes to simplifying the workflow by eliminating unnecessary processes.

[luke-]

@yurabakhtin Can you please check the tests?

[luke-]

@yurabakhtin hm, still something broken :-)

[yurabakhtin]

@luke- Now it is fixed.