Prevent usage of node or browser APIs in @segment/analytics-core and @segment/analytics-node

[silesky]

1. Remove isOffline() from core
2. eslint error if any native node modules are used.
3. eslint error any of the following are used in source code of core/node (since isomorphic):
   'document',
   'window',
   'self',
   'process',
   'global',
   'navigator',

[changeset-bot]

🦋 Changeset detected

Latest commit: 02c7ebf

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@segment/analytics-core	Patch
@segment/analytics-next	Patch
@segment/analytics-node	Patch

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[oscb]

This lgtm.

Correct me if I'm getting this wrong: packages/core is the isomorphic core whereas browser/core will retain the browser specific implementation, right?

[silesky]

This lgtm.

Correct me if I'm getting this wrong: packages/core is the isomorphic core whereas browser/core will retain the browser specific implementation, right?

Yep. and Analytics-node (despite the name) is also isomorphic.

Also some background: I plan to change the name from browser/core to browser/domain or something, since it's easy to find yourself in the wrong file when searching.