Rebrand: repository and external updates around 1.0.1 (operator) #1034

Part of #1024. Step 10, at and after the 1.0.1 publish.

• Repository About: description, website link, topics.
• Repository social preview image: rebranded hero.
• After publishing 1.0.1: check the Marketplace listing (name, description, README rendering) and the Q&A.
• aka.ms link titles that name the extension.
• Azure portal "Open in VS Code" text, if it names the extension.
• Azure Databases extension (vscode-cosmosdb): its own "moved to DocumentDB for VS Code" messaging.