Add 'wdm' to bundled CLI 2.x Gemfile

[Poitrin]

WHY are these changes introduced?

Fixes #780

WHAT is this pull request doing?

shopify-cli is using the gem listen, which calls require 'wdm', without having it mentioned in its Gemfile (→ guard/listen#553).

To solve this, we install wdm via the bundled CLI's Gemfile.

How to test your changes?

Windows

1. Open your Windows environment
2. Clone cli repo and cd into it
3. yarn install and yarn build
4. cd into a valid theme directory
5. Make sure that gem which wdm returns Can't find Ruby library file or shared library wdm
6. run node ../cli/packages/cli-main/bin/dev.js theme dev
7. (potentially log in into your store)
8. No error regarding wdm should appear anymore
9. Open C:\Users\<YOUR USER NAME>\AppData\Local\shopify-cli-nodejs\Cache\vendor\ruby-cli\<2.x.x>\Gemfile and make sure that gem 'wdm' is mentioned there

macOS

1. Repeat the same steps on macOS
2. Open /Users/<YOUR USER NAME>/Library/Caches/shopify-cli-nodejs/vendor/ruby-cli/<2.x.x>/Gemfile and make sure that gem 'wdm' is not mentioned there

Post-release steps

Measuring impact

How do we know this change was effective? Please choose one:

• n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've made sure that any changes to dev or deploy have been reflected in the internal flowchart.

[github-actions]

Thanks for your contribution!

Depending on what you are working on, you may want to request a review from a Shopify team:

• Themes: @shopify/theme-developer-tools
• UI extensions: @shopify/ui-extensions-cli
• Hydrogen: @shopify/hydrogen
• Other: @shopify/cli-foundations

[karreiro]

Thank you, @Poitrin! Great stuff 🚀 I've left only one minor comment/question :)

[karreiro]

Thank you, @Poitrin! LGTM and works fine as well 🎩

[Arkham]

LGTM!

[AaronGabriel147]

This update looks nice but I am slightly confised about 3 of the steps on Windows that are listed. What exactly do these steps mean?

5. Make sure that gem which wdm returns Can't find Ruby library file or shared library wdm
6. run node ../cli/packages/cli-main/bin/dev.js theme dev
7. (potentially log in into your store)

[Arkham]

@AaronGabriel147 they are to test that this change is working correctly using the development version of the code. As a user you don't need to worry about them.