Added explanation for package-lock-overrides folder (aws#27)

Author: aderende

README.md

@@ -6,6 +6,7 @@ This is the repo for `code-editor`.
 
 The repository structure is the following:
 - `overrides`: Non-code asset overrides. The file paths here follow the structure of the `third-party-src` submodule, and the files here override the files in `third-party-src` during the build process.
+- `package-lock-overrides`: Contains `package-lock.json` files to keep dependencies in sync with patched `package.json` files. These locally generated files ensure `npm ci` works correctly. They override corresponding files in `third-party-src` during build.
 - `patches`: Patch files created by [Quilt](https://linux.die.net/man/1/quilt), grouped around features.
 - `third-party-src`: Git submodule linking to the upstream [Code-OSS](https://github.com/microsoft/vscode/) commit. The patches are applied on top of this specific commit.