feat(plugin-sdk): add TypeScript SDK for Infinite Canvas plugins with automatic JSX and build support

plugins/canvas/markdown/src/env.d.ts

@@ -0,0 +1,10 @@
+// esbuild 以 text loader 把 .css 打成字符串
+declare module "*.css" {
+    const css: string;
+    export default css;
+}
+
+// 重依赖从 CDN 动态加载,不打进 bundle;此处声明以便 TS 提示
+declare module "https://esm.sh/marked@14" {
+    export const marked: { parse: (src: string) => string };
+}