Fix for "X zip is required for packaging a theme" on Windows

[mgmanzella]

WHY are these changes introduced?

Fixes https://github.com/Shopify/shopify-cli/issues/2513

WHAT is this pull request doing?

Modifies the package command to use a 7zip to zip files when theme package is run on Windows

How to test your changes?

Machine Setup

The test steps should be run on all platforms.

Mac

• Clone shopify-cli repo
• Add the following to ~/.zshrc and replace with your machine username:

  alias shopify-dev="/Users/<USERNAME>/src/github.com/Shopify/shopify-cli/bin/shopify"

Windows

• Clone shopify-cli repo and checkout branch with changes
• Change shopify.bat name in the bin folder of the repo to shopify-dev.bat
• Add the bin folder to the PATH
• Restart machine
• Confirm setup works by running shopify-dev version

Linux

TODO

Test Steps

1. If you don't have a theme available, shopify-dev theme init
2. shopify-dev theme package <path/to/theme>
3. Confirm zip file is generated in theme directory with theme name and version as the name
4. Unzip the zip file and confirm only directories in THEME_DIRECTORIES are present
5. Confirm nested folders were also included
6. cd <theme-name>
7. shopify-dev theme package
8. Repeat steps 3-5

Post-release steps

• Open issue in shopify-dev to update theme package docs to indicate we only support 7zip for theme package on windows

Update checklist

• [x] 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).
• [x] I've left the version number as is (we'll handle incrementing this when releasing).
• [x] I've included any post-release steps in the section above (if needed).