feat: Add Semantic Text Splitter

[promentol]

Added semantic text splitter, similar to python version
I put the file in experimental folder, as in python version it is still in langchain_experimental package

solves this https://github.com/langchain-ai/langchainjs/discussions/7147

Do we need to update documentation too, if approved?

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2 Skipped Deployments

Project	Deployment	Preview	Comments	Updated (UTC)
langchainjs-api-refs	Ignored			Oct 14, 2025 9:19am
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[hntrl]

Hey @promentol! Thanks for the change

I'll call out that we're about to merge v1, which significantly alters the package structure of langchain. Would you mind rebasing your changes onto there, and fitting this into libs/langchain-textsplitters? (we aren't exporting text splitters from the langchain package anymore)

[promentol]

@hntrl Thank you for feedback, I am closing this PR and issued new one for v1 branches

#9199