Hello this is my submission for the Github Actions hackaton!
I actually developed this for my organization but it is really useful for installing private npm modules (in this case hosted on github)
You gotta pass these inputs:
org_name
Organization name (Github repository name)

auth_token
AuthToken that is able to download files from the repository, can also be passed as env and it's rather recommended this way

And you use it like in the example on below

My Workflow

name: core

on:
  pull_request

jobs:
  continous-integration:
    runs-on: ubuntu-latest

    strategy:
      matrix:
        node-version: [12.x]

    steps:
      - uses: actions/checkout@v2
      - name: Use Node.js ${{ matrix.node-version }}
        uses: actions/setup-node@v1
        with:
          node-version: ${{ matrix.node-version }}
      - name: Create a .npmrc file for the github private repository
        uses: FerLuisxd/create-npmrc@3
        with:
          org_name: lig0  
        env:
          AUTH_TOKEN: ${{ secrets.OGIL_PALOMA_SECRET }}
      - run: npm install
      - run: npm run lint
      - run: npm test
        env:
          CI: true

Submission Category:

DIY Deployments

Yaml File or Link to Code

uses: ferluisxd/create-npmrc@3
with:
  org_name: lig0
  auth_token: 31352d11daasdf769942919dsafas594a5d
  env:
    AUTH_TOKEN: ${{ secrets.github_auth_token }}

registry = https://npm.pkg.github.com/lig0
//npm.pkg.github.com/:_authToken=31352d11daasdf769942919dsafas594a5d

🎉 Congratulations, you have successfully automated your private module installs! 🎊

Additional Resources / Info

If you need to know more about installing private modules click (here)[https://docs.github.com/pt/packages/using-github-packages-with-your-projects-ecosystem/configuring-npm-for-use-with-github-packages]