doc: fix grammar and punctuation in buffer.md

[Rawal27]

Summary

This PR makes grammar, punctuation, and wording corrections across the buffer API documentation.

Changes

• Corrected grammatical errors and awkward phrasing.
• Fixed punctuation inconsistencies across parameter descriptions and explanatory text.
• Improved sentence structure while preserving the original technical meaning.
• Standardized wording where similar API descriptions use inconsistent phrasing.
• Corrected minor formatting issues in documentation text.

Documentation-only changes to improve the readability, consistency, and correctness of the buffer API documentation.

[aduh95]

Please stop opening PRs faster they can be reviewed. If you do not stop, you will get blocked from the organisation.

[Rawal27]

@aduh95 Can you clarify this? I mean, these are genuine doc-level changes that I have proposed. Also, a contributor can contribute to as many as 30 pull requests at a time. Closing them without reason seems unfair to me.

[Rawal27]