feat: allow React 17 peer dependency

[adidahiya]

Fixes #4391

Changes proposed in this pull request:

Allow React 17 as an NPM peer dependency for all packages.

Reviewers should focus on:

Despite Blueprint's usage of some legacy APIs (#4149, #3979, etc), React 17's breaking changes don't seem to affect our components, so I think it's ok to expand the allowed version ranges.

This PR does not change the repo to build with React 17 or test it out in CI workflows. If there are issues with React 17 compatibility in the future, we can flag those issues and work on resolving them incrementally.

Screenshot

Tested it out locally with a Yarn resolution set to 17.0.1:

[blueprint-bot]

Merge remote-tracking branch 'origin/develop' into ad/allow-react-17

Previews: documentation | landing | table

[jasongrout]

FYI, there still is a dependency on react-popper ^1:

blueprint/packages/core/package.json

Line 56 in 241b20d

"react-popper": "^1.3.7",

react-popper 1 has a peer dependency on react 16, so installing @blueprintjs/core still ends up with a warning for react 17 from it.

react-popper ^2 now has updated to have a peer dependency allowing react 17: floating-ui/react-popper#390

[jasongrout]

react-popper ^2 now has updated to have a peer dependency allowing react 17: popperjs/react-popper#390

It looks like #4488 upgrades to react-popper 2 (fixing #4023). Unfortunately, it seems that change will be released in an upcoming release, and doesn't fix the react 17 peer dependency compatibility problem with the current blueprint.

For those running into npm install errors with npm v7, installing with npm install --legacy-peer-deps lets the install proceed instead of erroring out.