docs: mention file limits for locale PRs (#2322)

CONTRIBUTING.md

@@ -42,6 +42,11 @@ If adding new data definitions to Faker, you'll often need to find source data.
 - But if you are compiling a list of, for example, popular personal names or cities, don't copy directly from a single source (Wikipedia, 'most popular' articles, government data sites etc). A compilation of facts [can be copyrighted](https://en.wikipedia.org/wiki/Copyright_in_compilation).
 - It's best to refer to multiple sources and use your own judgement/knowledge to make a sample list of data.
 
+## Adding new locale or updating existing one
+
+After adding new or updating existing locale data, you need to run `pnpm run generate:locales` to generate/update the related files.
+If you change more than 20 locale files, please consider splitting your PR into one per category (e.g. person, location).
+
 ## Building Faker
 
 The project is being built by [esbuild](https://esbuild.github.io) (see [bundle.ts](scripts/bundle.ts))
@@ -163,10 +168,6 @@ describe('someModule', () => {
 });
 ```
 
-## Adding new locale or updating existing one
-
-After adding new or updating existing locale data, you need to run `pnpm run generate:locales` to generate/update the related files.
-
 ## Deprecation workflow
 
 If you ever find yourself deprecating something in the source code, you can follow these steps to save yourself (and the reviewers) some trouble.