Better dual ESM/CJS support, tsconfig module now Node16, improved pnpm support

Update Module and ModuleResolution to Node16 in tsconfig.
- This is what FluidFramework is doing for their default tsconfig's
- FF expects that all customers update TS configuration to use Node16+ compatible resolution.
- example: "module": "Node16" + "moduleResolution": "Node16"
- For apps, they often want "module": "ESNext" + "moduleResolution": "Bundler"
Add .js extensions throughout code.
export package.json override on CJS builds for {type: commonjs}
Added resolution support for @microsoft/live-share/internal for Node10.
- ESM only for Node10, CJS not supported. This matches FF.
update live-share-acs, live-share-canvas, live-share-react to ship CJS and ESM builds.
update live-share index to not have a root index, just index.public.ts and index.internal.ts
updated dependencies and peerDependencies.
- Improved pnpm support #745
- Moved some dev dependencies to direct dependencies
Added a pnpm project, and a CI check to ensure that Live Share works and is simple to use with pnpm

microsoft / live-share-sdk