This commit adds the possibility to provide to the caching component data already known and to be
cached immediately without the need of a callback function. This allows caching individual
repositories without having to rely on additional API calls. However, repos can also be retrieved
individually from the GitHub API based on their full name.
This commit removes the PreviewImage component that hasn't been used for quite some time in the
codebase.
BREAKING CHANGE: deletion of PreviewImage component
