fix: Support ESM in Node.js through conditional exports

[steve-taylor]

This is an attempt to fix #3601. This fix uses conditional exports and is specifically to fix how Node.js, not bundlers, import styled components.

I'm leaving it as a draft for now, because it's not fully tested due to @emotion/is-prop-valid possibly suffering from the same issue and needing the same fix:

TypeError: i is not a function
    at file:///path/to/repo/node_modules/styled-components/dist/styled-components.esm.mjs:1:20617
    at x (file:///path/to/repo/node_modules/styled-components/dist/styled-components.esm.mjs:1:20841)
    at Wc (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:68:44)
    at Zc (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:73:362)
    at Z (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:76:89)
    at $c (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:78:98)
    at bd (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:77:404)
    at Z (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:76:217)
    at $c (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:78:98)
    at Zc (/path/to/repo/node_modules/react-dom/cjs/react-dom-server.browser.production.min.js:71:145)

i is the default export from @emotion/is-prop-valid.

Similarly, in my (legacy) v5 backport, I had this issue with @emotion/stylis:

TypeError: h is not a constructor
    at ae (file:///path/to/repo/node_modules/styled-components/dist/styled-components.esm.mjs:1:12214)
    at file:///path/to/repo/node_modules/styled-components/dist/styled-components.esm.mjs:1:13205
    at ModuleJob.run (node:internal/modules/esm/module_job:198:25)
    at async Promise.all (index 0)
    at async ESMLoader.import (node:internal/modules/esm/loader:385:24)
    at async importModuleDynamicallyWrapper (node:internal/vm/module:437:15)

h is the default export from @emotion/stylis.

When I get some time later in the week, I'll work my way through the affected Emotion packages and, if that ultimately fixes the problem, create additional PRs to support this one.

[steve-taylor]

This is a deep rabbit hole. My Emotion PR was summarily closed in favour of a larger competing PR that needs some work and relies on a Preconstruct PR.

[wight554]

This is a deep rabbit hole. My Emotion PR was summarily closed in favour of a larger competing PR that needs some work and relies on a Preconstruct PR.

https://github.com/sheremet-va/dual-packaging might be helpful

[patsplat]

It appears that the larger competing PR was closed, recreated, and has now merged.

[patsplat]

I am another user impacted by this bug.

How can I help test this fix? What steps should I take to do so?

[dexbol]

Hope this PR would merge to v6.

[quantizor]

Added "exports" to package json in the most recent beta that should help with this