chore: add svelte component layer with monaco editor

src/theme-svelte.d.ts

@@ -0,0 +1,5 @@
+// The internal client module is intentionally untyped in Svelte's package
+// exports. Theme components only need its namespace at runtime, so treat it as
+// an opaque module rather than importing private implementation types.
+declare module 'svelte/internal/client';
+declare module 'svelte/internal/flags/legacy';