* Add repo metadata, start with categories!
scripts for checking repo categories, updating the canonical set
added categories to push.pl
* Add initial set of semi-acurate categories
* Adjustments following tianon's review
* Simplify metadata.sh use cases (CI or interactive); just diff and check all the time
Update README.md about metadata.sh usage
* Unify the categories checks into one jq expressions
* Update initial categories
* Link to Docker docs for categories; minor categories script adjustments
William Desportes