Docs improvements

[tudorpintea999]

Hello!
During reading the docs, my OCD observed some minor typos that I fixed.
Hope it helps,
Br,
Tudor

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PR-Codex overview

This PR focuses on correcting minor grammatical issues across various documentation files related to the Farcaster framework, improving clarity and readability.

Detailed summary

• Changed "Returns an error if URI is invalid." to "Returns an error if the URI is invalid." in parse-sign-in-uri.md.
• Corrected "potential dangerous" to "potential dangers" in spec.md.
• Updated "ready to displayed" to "ready to be displayed" in v2/spec.md.
• Changed "Frames v2 allow" to "Frames v2 allows" in notifications_webhooks.md.
• Fixed "a a way" to "a way" in index.md.
• Corrected "on Github" to "on GitHub" in getting-started.md.
• Updated "insert an click-through" to "insert a click-through" in getting-started.md.

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