docs(config): document precedence order of config files (#13447)

docs/usage/configuration-options.md

@@ -10,15 +10,19 @@ Any config you define applies to the whole repository (e.g. if you have a monore
 
 You can store your Renovate configuration file in one of the following locations:
 
-- `.github/renovate.json`
-- `.github/renovate.json5`
-- `.gitlab/renovate.json`
-- `.gitlab/renovate.json5`
-- `.renovaterc.json`
-- `renovate.json`
-- `renovate.json5`
-- `.renovaterc`
-- `package.json` _(within a `"renovate"` section)_
+1. `renovate.json`
+1. `renovate.json5`
+1. `.github/renovate.json`
+1. `.github/renovate.json5`
+1. `.gitlab/renovate.json`
+1. `.gitlab/renovate.json5`
+1. `.renovaterc`
+1. `.renovaterc.json`
+1. `package.json` _(within a `"renovate"` section)_
+
+_Note_: Storing the Renovate configuration in a `package.json` file is deprecated and support may be removed in the future.
+
+When renovating a repository, Renovate will try to detect the configuration files in the order listed above, and stop after the first one is found.
 
 Renovate always uses the config from the repository's default branch, even if that configuration specifies multiple `baseBranches`.
 Renovate does not read/override the config from within each base branch if present.