Add Walrus integration docs to Suibase website

[mario4tier]

Proposing the following changes:

(1) Add a new page named "Integration" under the "Suibase Docs" section. (2) Add a "Walrus" section ( https://github.com/MystenLabs/walrus-sites/issues/94 )

[mario4tier]

@kkomelin an integration page has been added ( https://suibase.io/how-to/integration ). Do you want to fill the Walrus section? (if yes, then just proceed at your convenience with the "edit" button on the page).

[kkomelin]

Sure. Thank you @mario4tier. I will do