fix: check for document existence to support React Native

[Br1an67]

Fixes #1017

Summary

Fixed a ReferenceError that occurred when using anime.js in React Native environments. React Native has a window object but does not have a document object, which caused the library to throw "Property 'document' doesn't exist" error on import.

Changes

• Added an explicit check for document existence in src/core/consts.js before accessing it
• Changed export const doc = isBrowser ? document : null; to export const doc = isBrowser && typeof document !== 'undefined' ? document : null;

Testing

Verified that the JavaScript parses correctly. This is a minimal, surgical fix that only affects the document detection logic.

$ git diff --stat HEAD~1
src/core/consts.js | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

[juliangarnier]

isBrowser should return false in non browser environment. I don't like having this double check "is browser + document is undefined", can you update the isBrowser variable instead?