Ensure correct ngrok version is downloaded for Apple M1

[stevemar]

This patch adds support for installing the proper version of
ngrok when running shopify app serve on M1 macs.

Specifically, this patch updates the os property of the shop-cli
context with a new key mac_m1, not just mac, and updates the
DOWNLOAD_URL dictionary.

Fixes #1785

How to test your changes?

Pull down the branch, install it locally, create a new app and try to serve it..

bundle install
bundle exec shopify app create node
bundle exec shopify app serve

As discussed in the bug, previously the ngrok tunnel step would fail.

➜  test-m1 git:(m1-support) ✗ bundle exec shopify app serve    
⭑ You are running a development version of the CLI at:
  /Users/stevemartinelli/workspace/stevemar/shopify-cli/bin/shopify
✓ curl @ /usr/bin/curl
✓ tar @ /usr/bin/tar
✓ Installing ngrok…
✓ ngrok tunnel running at https://fd15-76-68-94-203.ngrok.io
⭑ To avoid tunnels that timeout, it is recommended to signup for a free ngrok
account at https://ngrok.com/signup. After you signup, install your
personalized authorization token using shopify [ node | rails ] tunnel auth <token>.
✓ .env saved to project root

Verifying change

The new version is arm64 based

➜  shopify-cli git:(m1-support) ✗ lipo -info ~/.cache/shopify/ngrok 
Non-fat file: /Users/stevemartinelli/.cache/shopify/ngrok is architecture: arm64

The old version was not

➜  test-m1 git:(m1-support) ✗ lipo -info ~/.cache/shopify_bak/ngrok
Non-fat file: /Users/stevemartinelli/.cache/shopify_bak/ngrok is architecture: x86_64

Update checklist

• I've added a CHANGELOG entry for this PR (if the change is public-facing)
• I've considered possible cross-platform impacts (Mac, Linux, Windows).
• I've left the version number as is (we'll handle incrementing this when releasing).
• I've included any post-release steps in the section above.

[pepicrft]

This is amazing @stevemar 👏🏼 . Would you mind updating the CHANGELOG.md to mention that we fixed an issue that causes Ngrok tunneling to fail? After that and if CI is green we can merge.

[stevemar]

@pepicrft thanks for reviewing! As requested, I updated the CHANGELOG to note the change. In case you're wondering, I had to close and re-open the PR to clear the CLA label since I just joined the org.

[pepicrft]

Thanks a lot, @stevemar. Let's merge this and get it released in the next version that goes out next Monday, December 13th. Keep those great contributions landing 🚀