ESM: use .js extension with type: module in package.json

[denysoblohin-okta]

Better way to fix ES module for Node.js and browser environments and also for using with Jest:

• Keep '.js' extension instead of '.mjs'
• Add small 'package.json' file to dist/esnode and dist/esbrowser with contents { "type": "module" }

Without this change need to use moduleNameMapper in Jest config with entry:

'^broadcast-channel$': '<rootDir>/node_modules/broadcast-channel/dist/esnode/index.mjs'

[denysoblohin-okta]

@pubkey Any thoughts on PR?

[pubkey]

@denysoblohin-okta does this conflict with your pr #962 ?

To be honest, I have no personal opinion, I have just given up on ever having 'standard' way to distribute browser&node npm modules. The correct way changes once a year and you will always find a build tool that is not compatible with how the code is distributed.

Shouldn't this be a PR to Jest because they should support mjs files?

[denysoblohin-okta]

It does not conflict with #962, it does the same thing but with support of how Jest resolves ES modules

[pubkey]

Merged and released in 4.13.0