List the labels defined in a GitHub repository: name, color, description, whether it is one of GitHub's nine default labels, and a link to the label page. Use it when the user asks what labels a repo has, how many labels it has, or which labels mention a word. Optional case-insensitive filter over name and description, optional alphabetical sort, optional cap. It reads github.com's own labels route from an open github.com tab, so there is no token to supply and no API rate limit. For the labels attached to issues, use github-list-issues instead: that one reports the labels in use, this one reports the label set the repo defines.