chore: set repository.directory to all sub package.json files

[ybiquitous]

Hi there,

I've created this PR to make npm commands such as npm repo more useful.
For example, all packages in the Babel repository have that field (babel/babel#11625).

This change sets the repository.directory field to all package.json files except for package.json at the repository root.

See also https://docs.npmjs.com/cli/v7/configuring-npm/package-json#repository

How to create this change

I've created the following Bash script for this PR:

#!/usr/bin/env bash
set -eu -o pipefail

files=$(git ls-files | grep package.json)
for file in $files; do
  echo "Setting repository.directory to ${file} ..."
  dir=$(dirname $file)
  if [[ $dir != "." ]]; then
    (cd "$dir" && npm pkg set repository.directory="$dir")
  fi
done

In addition, I've used the command npm-package-json-lint to verify this change as below:

.npmpackagejsonlintrc.json:

{
  "rules": {
    "require-repository-directory": "error"
  }
}

Run:

$ npx npm-package-json-lint .

./package.json
✖ require-repository-directory - node: repository - repository object missing directory property
1 error
0 warnings

Totals
1 error
0 warnings
0 files ignored

Note: package.json at the top should not have directory, so the error above is expected.

---

I would appreciate it if you could check this PR.
If this PR is undesirable, please feel free to close it. Thank you. 😃