feat: github action for republishing of mysten sites

[Tzal3x]

Description

Whenever there is an update to the smart contract source code (not the tests), we should set up a github action that does the following:

• Republishes the contract.
• Publishes all (maybe except flatland because of its' complexity) to the mysten-owned sites from https://github.com/MystenLabs/example-walrus-sites.
• Re-assigns the SuiNS names to the newly deployed sites.

Component

other

Code of Conduct

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