fix: resolve npm peer dependency conflicts

[LayaTaal]

Summary

• Adds overrides block to package.json to pin react and react-dom to ^18.0.0, preventing npm from resolving React 19 (via @dnd-kit's loose >=16.8.0 peer dep) which conflicts with @wordpress/icons and @wordpress/scripts
• Ported from nexcess-2026#8

Test plan

• Delete node_modules and package-lock.json, then run npm install — should complete without errors
• Run npm run build to verify blocks compile successfully

🤖 Generated with Claude Code

[LayaTaal]

@dpellenwood @GeoffDusome I ran into this issue on the Nexcess site when trying to install fresh dependencies. NPM wants to automatically go to React 19 which is causing issues with the WordPress icon library peer dependency requirement.

I'm not sure why the extra minimatch override was originally included, but I have removed that without issue.

[dpellenwood]

@dpellenwood @GeoffDusome I ran into this issue on the Nexcess site when trying to install fresh dependencies. NPM wants to automatically go to React 19 which is causing issues with the WordPress icon library peer dependency requirement.

I'm not sure why the extra minimatch override was originally included, but I have removed that without issue.

Note that this issue is only applicable if there is not a package-lock.json file present. I was able to get around this by running npm i --legacy-peer-deps and then any subsequent npm install runs are fine. I'm not sure I want to commit this to the project right away. I would like to see if we can give it a bit of time so that all our deps can bump to React 19.