Context

The MR !8637 (merged) that introduces octez-libs removed the synopsis from libraries that where included as sub-libraries.

This MR adds these synopsis back as description in the doc page of octez-libs

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Manually testing the MR

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Document the interface of any function added or modified (see the coding guidelines)
Document any change to the user interface, including configuration parameters (see node configuration)
Provide automatic testing (see the testing guide).
For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
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