docs: add missing space in examples sentence

[scosemicolon]

Fixes a small README formatting typo by adding a missing space after the comma before LangChain.

No code changes.

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[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}