Add missing result-cache folder in tooling-integration document

Author: jfmengels

documentation/tooling-integration.md

@@ -17,6 +17,7 @@ The CLI creates a bunch of cache inside `elm-stuff/generated-code/jfmengels/elm-
 
 - `file-cache/`: Caching of the file's ASTs.
 - `review-applications/`: Caching of the project's configuration. This is the application we build by compiling the source code in the CLI's `template/` directory.
+- `result-cache/`: Caching of the results of each module's analysis for every rule.
 - `dependencies-cache/`: Caching of the dependencies of the project's configuration computed by `elm-json`. `elm-json` is a bit slow, and doesn't work great offline. This is done so we don't have to compute the dependencies again if the configuration changed but not `review/elm.json`.
 - `elm-parser/`: Caching of the parser application. This is the application we build by compiling with the user's version of `stil4m/elm-syntax`, and the name of the file reflect the version. This is used to parallelize the parsing of the files, which is kind of slow, at startup.