docs(usage): clarify that packageRules must have a selector (#31512)

Co-authored-by: Rhys Arkins <[email protected]>

docs/usage/configuration-options.md

@@ -2414,14 +2414,13 @@ The order of rules matters, because later rules may override configuration optio
 
 The matching process for a package rule:
 
-- Each package rule can include `match...` matchers to identify dependencies and `exclude...` matchers to filter them out.
-- If no match/exclude matchers are defined, everything matches.
-- If an aspect is both `match`ed and `exclude`d, the exclusion wins.
-- Multiple values within a single matcher will be evaluated independently (they're OR-ed together).
-- Combining multiple matchers will restrict the resulting matches (they're AND-ed together):
-  `matchCurrentVersion`, `matchCurrentValue`, `matchNewValue`, `matchConfidence`, `matchCurrentAge`,
-  `matchManagers`, `matchDatasources`, `matchCategories`, `matchDepTypes`, `matchUpdateTypes`,
-  `matchRepositories`, `matchBaseBranches`, `matchFileNames`
+- Each package rule must include at least one `match...` matcher.
+- If multiple matchers are included in one package rule, all of them must match.
+- Each matcher must contain at least one pattern. Some matchers allow both positive and negative patterns.
+- If a matcher includes any positive patterns, it must match at least one of them.
+- A matcher returns `false` if it matches _any_ negative pattern, even if a positive match also occurred.
+
+For more details on positive and negative pattern syntax see Renovate's [string pattern matching documentation](./string-pattern-matching.md).
 
 Here is an example if you want to group together all packages starting with `eslint` into a single branch/PR: