fix: update React and ReactDOM versions in peerDependencies

[Almaju]

Because this library is consumed by other apps, we want react to be listed as a peer dependency to let the main app manage the version. We use >= 19.0.0 not to be restrictive with the minor and patch versions.
We also add it to the devDependencies to be able to use React in tests.
I took inspiration of other open source JS libraries (example: https://github.com/mobxjs/mobx-react-lite/blob/master/package.json or https://github.com/Effect-TS/effect/blob/main/packages/rpc/package.json).

[justindarc]

Can you also update the React example in /examples to pull a different React version to demonstrate that this is now working as we intend. I think doing this will also make it can act as a basic smoketest with our integration testing if the React example fails to build.

[Almaju]

Can you also update the React example in /examples to pull a different React version to demonstrate that this is now working as we intend. I think doing this will also make it can act as a basic smoketest with our integration testing if the React example fails to build.

@justindarc I tested different React versions in examples/react/package.json and then npm i with both >= 19.0.0 and previous versions. I correctly have only one react dependency in node_modules at the end but this might need to be tested against the published npm package (instead of a local path in tsconfig).

In case of a version mismatch, it gets overridden by npm with a warning:

npm warn ERESOLVE overriding peer dependency
npm warn While resolving: @mozilla/majc-react-example@0.1.0
npm warn Found: react@19.0.0
npm warn node_modules/react
npm warn   react@"18.0.0" from the root project
npm warn   3 more (next, react-dom, styled-jsx)

Not sure what I should commit specifically in the React example to demonstrate that it works since the peerDependencies specifies >= 19.0.0 which would work with any version currently compatible with Nextjs 15.

[justindarc]

Good call. Let's go with this for now, get it merged, then we can publish and do a follow-up PR if possible to demonstrate what we were trying to do. Thanks for looking into it!