Fix grammar and readability in README.md

[Copilot]

Fix grammar issues and improve scannability of README.md.

• Comma splices: Split run-on sentences in Installation ("…locally, install it…") and disabledLintKinds ("…to filter out, available kinds:")
• Trailing punctuation: Add missing periods to all config option list items
• Wording: "very big" → "large", "persisted at" → "stored at", "Presets disable" → "Each preset disables"

Original prompt

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This section details on the original issue you should resolve

<issue_title>README.md</issue_title>
<issue_description>Improve the overall README.md, the goal is to fix grammar issues, make it easier to follow.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes README.md #20

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