Add tskm playground

[ushironoko]

Summary

• add a Vite React playground under playgrounds/tskm
• add Shiki-based schema/input/result highlighting with tskm schema/action/method call highlighting
• add generated type preview and JSON input typechecking with inline diagnostics

Verification

• bunx biome check playgrounds/tskm package.json
• bun run --cwd playgrounds/tskm build
• verified editor caret/selection, hover states, typecheck diagnostics, and console output with playwright-cli

[pkg-pr-new]

Open in StackBlitz

bun add https://pkg.pr.new/@tskm/compiler@5c48d1c

bun add https://pkg.pr.new/@tskm/core@5c48d1c

bun add https://pkg.pr.new/@tskm/vite@5c48d1c

commit: 5c48d1c