github: document auth input options

[benbroadaway]

No description provided.

[Copilot]

Pull Request Overview

Adds documentation for new GitHub task authentication options supporting GitHub App installations and token creation.

• Replaces single accessToken parameter with a unified auth object supporting accessToken, appInstallation, and appInstallationSecret.
• Introduces detailed auth examples and new createAppToken action usage.
• Updates multiple task call examples to use auth consistently.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
docs/plugins-v2/git.md	Updates parameter list to use auth, adds examples and createAppToken section.
docs/plugins-v1/git.md	Mirrors v2 updates for auth parameter and examples; adds Common Task Parameters section.

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