docs: add read-collections and write-collections OAuth scopes

[alexpouliquen]

Add two new OAuth scopes: read-collections and write-collections

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Note

Low Risk
Low risk documentation-only change that just exposes two additional OAuth scope names in the supported-scope lists.

Overview
Documents two new OAuth scopes for collections access. Updates the supported scope lists in docs/hub/oauth.md and docs/hub/spaces-oauth.md to include read-collections and write-collections, describing their read vs. write/create/delete permissions for user collections.

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[HuggingFaceDocBuilderDev]

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[Pierrci]

nice, thanks!