Add GPU edge node manege docs

[wbc6080]

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Which issue(s) this PR fixes:

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• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

docs update

• What is the new behavior (if this is a feature change)?

Added documentation for managing edge GPU nodes and introduce how to use GPU resources in edge applications.

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[tangming1996]

/lgtm

[kubeedge-bot]

New changes are detected. LGTM label has been removed.