backlink to language docs for customized analysis

Follow up from: https://github.com/dart-lang/linter/issues/1365.


Change-Id: Iaeef849406b191d99a84501884c3d34b37ccb59d
Reviewed-on: https://dart-review.googlesource.com/c/91681
Commit-Queue: Phil Quitslund <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: pq

pkg/analyzer/README.md

@@ -64,6 +64,9 @@ linter:
     - camel_case_types
 ```
 
+For more information, see the docs for
+[customizing static analysis][custom_analysis].
+
 ## Who uses this library?
 
 Many tools embed this library, such as:
@@ -104,3 +107,4 @@ See the [LICENSE] file.
 [dartfmt]: https://github.com/dart-lang/dart_style
 [dartdoc]: https://github.com/dart-lang/dartdoc
 [analysis_sever]: https://github.com/dart-lang/sdk/tree/master/pkg/analysis_server
+[custom_analysis]: https://www.dartlang.org/guides/language/analysis-options