fix: declare @types/react as optional peer dependency

[adidahiya]

Changes proposed in this pull request:

Add @types/react as an optional peer dependency in package.json for each package that depends on those types in its generated .d.ts files.

This is in line with the approach taken by other modern OSS React UI library packages like @mui/material and react-bootstrap.

Reviewers should focus on:

If this actually fixes the problem we've been having in PNPM installs, where sometimes @types/react is not available to @blueprintjs/core to compile with tsc with skipLibCheck: false.

[adidahiya]

I'm going to push this for now, at least to signal to users that we have a minimum version of @types/react required to compile with Blueprint, but we'll need to keeping thinking about more solutions to the pnpm install problem.

[lavrton]

Can you increase version range?
Material UI: "@types/react": "^17.0.0 || ^18.0.0",
React bootstrap: "@types/react": ">=16.14.8",.

Currently, I have this error when I install the last blueprint in react@18 project.

npm ERR! code ERESOLVE
npm ERR! ERESOLVE could not resolve
npm ERR!
npm ERR! While resolving: @blueprintjs/core@4.9.2
npm ERR! Found: @types/react@18.0.17
npm ERR! node_modules/@types/react
npm ERR!   dev @types/react@"^18.0.17" from the root project
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peerOptional @types/react@"^16.14.2" from @blueprintjs/core@4.9.2
npm ERR! node_modules/@blueprintjs/core
npm ERR!   @blueprintjs/core@"^4.9.2" from the root project
npm ERR!   @blueprintjs/core@"^4.9.2" from @blueprintjs/popover2@1.6.2
npm ERR!   node_modules/@blueprintjs/popover2
npm ERR!     @blueprintjs/popover2@"^1.6.2" from the root project
npm ERR!     1 more (@blueprintjs/select)
npm ERR!   1 more (@blueprintjs/select)
npm ERR!
npm ERR! Conflicting peer dependency: @types/react@16.14.30
npm ERR! node_modules/@types/react
npm ERR!   peerOptional @types/react@"^16.14.2" from @blueprintjs/core@4.9.2
npm ERR!   node_modules/@blueprintjs/core
npm ERR!     @blueprintjs/core@"^4.9.2" from the root project
npm ERR!     @blueprintjs/core@"^4.9.2" from @blueprintjs/popover2@1.6.2
npm ERR!     node_modules/@blueprintjs/popover2
npm ERR!       @blueprintjs/popover2@"^1.6.2" from the root project
npm ERR!       1 more (@blueprintjs/select)
npm ERR!     1 more (@blueprintjs/select)

[adidahiya]

Sure thing @lavrton, will do ASAP