Track repository layout refactors for website, VS Code Web, docs and WASM artifacts

[kunlinglio]

The current repository layout mixes website, playground, VS Code Web, docs, and shared browser WASM build artifacts in ways that make their responsibility confusing.

This issue tracks the related repository layout refactors.

Tasks

• refactor(website): move docs/ and playground/ into website/ #304
• refactor(vscode): move packages/ shared code into vscode extension #306
• refactor(wasm): make vide-lsp-wasm own build script and artifacts #308
• Add real docs directory with simple develop documents structure.