Use relative path for example (#33565)

The paths starting with slashes in the ESLint config examples are absolute, which are almost never the correct configuration for a project. Using a relative path is a much more common configuration, and leads to much less debugging why these examples don't work.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`

Author: karlhorky

docs/basic-features/eslint.md

@@ -114,13 +114,13 @@ If you're using `eslint-plugin-next` in a project where Next.js isn't installed
   "extends": "next",
   "settings": {
     "next": {
-      "rootDir": "/packages/my-app/"
+      "rootDir": "packages/my-app/"
     }
   }
 }
 ```
 
-`rootDir` can be a path (relative or absolute), a glob (i.e. `"/packages/*/"`), or an array of paths and/or globs.
+`rootDir` can be a path (relative or absolute), a glob (i.e. `"packages/*/"`), or an array of paths and/or globs.
 
 ## Linting Custom Directories and Files
 

errors/no-html-link-for-pages.md

@@ -53,7 +53,7 @@ In some cases, you may also need to configure this rule directly by providing a
 ```json
 {
   "rules": {
-    "@next/next/no-html-link-for-pages": ["error", "/my-app/pages/"]
+    "@next/next/no-html-link-for-pages": ["error", "packages/my-app/pages/"]
   }
 }
 ```